In the spirit of Geoff Pullum's lyrical prescriptive poppycock offering, I can offer some Raymond Chandler in verse and letter. And this being Language Log, I will follow it with a light dessert of cheap science. Here's a small sample of Chandler's 1947 poem Lines to a Lady With an Unsplit Infinitive for your edification:
There ain't no grammar that equals a hammer
To nail down a cut-rate wit.
And the verb 'to be' as employed by me
Is often and lightly split.
A lot of my style (so-called) is vile
For I learned to write in a bar.
The marriage of thought to words was wrought
With many a strong sidecar.
The poem was at the expense of an overzealous proofreader at the Atlantic Monthly, and has been making the blog-and-other-social-media rounds for a few months, after Letters of Note picked up on it — see the full post here. And here's the letter to the magazine's editor which the poem accompanied (text taken from Letters of Note). Be careful, as it might cut through the glass on your ipad:
6005 Camino de la Costa La, Jolla, California Jan. 18th, 1947
Dear Mr. Weeks:
I'm afraid you've thrown me for a loss. I thought "Juju Worship in Hollywood" was a perfectly good title. I don't see why it has to be linked up with crime and mystery. But you're the Boss. When I wrote about writers this did not occur to you. I've thought of various titles such as Bank Night in Hollywood, Sutter's Last Stand, The Golden Peepshow, All it Needs is Elephants, The Hot Shop Handicap, Where Vaudeville Went it Died, and rot like that. But nothing that smacks you in the kisser. By the way, would you convey my compliments to the purist who reads your proofs and tell him or her that I write in a sort of broken-down patois which is something like the way a Swiss waiter talks, and that when I split an infinitive, God damn it, I split it so it will stay split, and when I interrupt the velvety smoothness of my more or less literate syntax with a few sudden words of barroom vernacular, this is done with the eyes wide open and the mind relaxed but attentive. The method may not be perfect, but it is all I have. I think your proofreader is kindly attempting to steady me on my feet, but much as I appreciate the solicitude, I am really able to steer a fairly clear course, provided I get both sidewalks and the street between.
If I think of anything, I'll wire you.
Of course, Language Log not just a place for acerbic poetry and prose takedowns of prescriptivists. So here is the cheap science I promised, a Google n-gram graph showing a broad rise over the last 60 years in the rate of split infinitives in books (red and blue lines) as against a fall in competing un-split forms:
I used trigrams like "him to always", as in "I wanted him to always love me". The graph starts in 1950, and the green and yellow lines show a decrease (as a % of all trigrams) in the use of the trigrams "him always to" and "him quickly to", respectively, through the second half of the twentieth century. The decline was apparently arrested as the new millenium began. A significant part in that late 20th century decrease was offset by increases in the split infinitive forms "him to always" (blue) and "him to quickly", which are now vastly more common in books than they were 60 years ago.
We can play the same game with slightly different n-grams. Here are Google n-gram comparisons of "always to be"/"to always be"/"to be always", and "always to have"/"to always have"/"to have always". With a bunch of different searches, I've generally seen the same pattern, namely clear increase in the split infinitive form (though for some verb / adverb combinations, the split infinitive remains very rare in this book sample) over the last 60 years, sometimes with a leveling off or drop at the end of the sample period. Of course, nothing else is quite as dramatic as the graph for "to boldly go".
OK, last graph. The blue line here shows what's been happening to the use in books of the term "split infinitive" from 1800 until 2008: You see that people started using the term at the end of the 19th century. It was climbing well before Strunk first published "The Elements of Style" in 1918, and reached its peak a few years later. For comparison, I've also included "start with and" (green), "who or whom" (red) and "stranded preposition" (yellow). So we're well past the heyday of split infinitive discussion. It's been relatively stable for the last 40 years as a perennial book topic, though whether the books are pro- or anti- will have to await some reader's future studies.
As regards the actual usage of split infinitives, is it possible that they're now in decline? Unfortunately, the n-gram corpus stops at 2008, so if you want to know the answer, you'll have to watch this space for another decade, or maybe a couple. For the moment, my take-home message is that whatever infinitives Chandler split may well have been daring when he split them, at least for books, if not for the bars he frequented. But it looks to me like infinitives are indeed likely to remain split for quite a while yet.