I've got to say - the whole timing fix thing from my perspective seems to be a big bucket load of codswallop. I've tried so many different accelerators on so many different A1200's and NEVER had to be concerned with timing fixes of any kind. Yes, logically this may be just entirely co-incidental in that all the 1200's I've had over the years have been timing fixed without me knowing it, or I've been lucky...who knows. I've tried PPC's, 1260's, ACA's, Apollo's and so on. Different revision motherboards. Demos, games, music, graphics, workbench proggies. Not a problem due to any lack of a "timing fix". I'll admit I've never looked into it from a technical perspective, as to why it might be needed, but maybe the whole timing fix thing is just an 'ol wives tale? Is there something specific to the 1200 that makes it that no other Amiga model needs timing fixes also? Because noone ever says "Oh...the Mtec 68020 needs a Rev 6 motherboard with timing fixes" - why not? Go figure...
On a similar note being a trade qualified mechanic I was O V E R people commenting about batteries being stored on cement, and how it damages them. Absolutely over it. Noone could ever say why. Or how long it took. Or exactly why it damaged them. But yet somehow everybody seemed to know that it damaged them! So, in short, I performed a "scientific" test over a period of 6 months using 4 brand new identical batteries under controlled conditions and my conclusion was that it was an absolute myth!
Disclaimer: Just my findings 
Well - back in the day with my Apollo 040 40mhz it was constantly crashing (and hadn't with the 28mhz blizzard). Sent for a timing fix and it never crashed again. My understanding is only certain revisions of motherboards (I think early Commodore ones) need the fix and only 040+ accelerators. it certainly is not a myth!
