just last month my r-12 suddenly quit working one day, i took it to a shop that had "r-12" and he had to rebuild one of my lines to the compressor, filled the system and charged my 240.00. he told me i still had a leak around the compressor and it was most likely the gasket under the plate held on by 4 allen bolts, so i ordered the compressor rebuild kit from watson (38.00) and replaced that gasket yesterday. so now i have to take it back and have it vacuumed and filled, hoping he doesn't find another leak. he told me it may last a year or a day, well, it lasted about an hour. for the last 6.5 years i've had my car, i had to put 2 cans of 12 in it, so it did leak about every 3 years i guess.
another local a/c shop told me it would cost 95.00 to convert over to 134, and i asked him what he was going to change and he mentioned nothing. i asked about seals and the dryer and he wondered where i was getting my info from, so i don't think he will ever get my business.