With examples from Good Omens.
Thanks, avidrosette! I enjoyed this question quite a lot.
The examples in your question are really helpful, but let’s still take a moment to explain what we’re talking about here. Regular (also called “weak”) past tense verbs are formed by adding -ed or -d to the present tense verb. So “walk” becomes “walked,” “lope” becomes “loped,” and so on. (Forms such as "admit">"admitted" and "carry">"carried" also count as regular even though the base form changes slightly before adding -ed.) Irregular past tense verbs (also called “strong”) form the past tense (or past participle) in ways other than that: often by changing the vowel (“sit” becomes “sat”), sometimes in a more dramatic fashion (“seek” becomes “sought”), sometimes by doing nothing at all (“hit” remains “hit” in either tense) and others that don’t seem to follow a pattern.
Then there is a small subset of past tense verbs that have both a regular and irregular form.
For centuries, Crowley and Aziraphale abided by the Agreement.
For centuries, Crowley and Aziraphale abode by the Agreement.
Which is correct? I could not find any rules governing when each form should be used. Perhaps, in part, because we are talking about a small fragment of the language. There are fewer than 200 irregular verbs in use in modern English (Bryan Garner, Garner’s Modern American Usage). Of those 200, only 20-some have both a regular and irregular form.
Because there are so few, if you are in doubt, I would recommend turning to that workhorse of reference materials, your favorite dictionary. Look up the base form of the verb, and you should see the inflected forms listed after it. Here’s an example from Merriam-Webster Online that shows the two options for past tense as well as the participial forms.
Main Entry: slay
Inflected Form(s): slew \ˈslü\ also especially in sense 2 slayed; slain \ˈslān\ ; slay·ing
The option listed first is the more commonly used or preferred form. If you want to make sure you don’t end up with readers mentally correcting you as they read, that one will usually be a safe bet. Since we’re talking about usage in flux though, also trust your own ear. And take advantage of the definition and any usage notes: many people get hung up on the past tense of "hang" — look for that Fandom Grammar entry next month.
You may also wish to use the regular past tense form as a characterization device in dialogue to convey dialect or when your speaker is a child. (As always, be careful not to overuse this device.)
The Them seemed unimpressed by the alleged fierceness of the bedraggled stray Pepper had discovered in her mother’s petunias the night before, so she used her most convincing spooky voice for the best part. “An’ when I shined my torch at him, his eyes glowed.”
“That’s nothin’,” Adam asserted. “Sometimes Dog’s eyes do that even when there ain’t any light.”
Dog thumped his tail and looked winsomely brown-eyed and harmless.
As to whether contemporary English usage is leaning more toward the regular forms, well, yes, but it’s a little more interesting than that.
We’ve commented in this community on some of the rather dramatic shifts in usage in today’s language. English has always been a living, evolving language, but it seems to be changing faster than ever these days. The irregular verbs, however, have been fading from usage for a very long time. In 1947, George Curme, author of English Grammar, remarked, “For many centuries there has been a steady loss [of irregular verbs] in favor of the weak class.”
But the irregular past tense is far from doomed. Many of the verbs we use most often are irregular. To name just a few: do, get, go, have, let, make, say, and of course the all-important be. Somehow I don’t see us making the transition from is/are, was/were and been to be and beed anytime soon.
And in a surprising sign of life for this steadily failing form, I can think of two verbs that have made the transition from regular to irregular in recent history. The past tense of “fit” used to always be “fitted,” but now it can be either "fitted" or "fit." The same is true of one of the very words given by avidrosette as an example. The past tense of “dive” is traditionally “dived.” However, probably because of its similarity to “drive,” which has a past tense of “drove,” we now are as likely to use the irregular “dove.”
In short, if a verb has both a regular and irregular form, you have the flexibility to use whichever sounds better to you or best conveys the voice you want.