R134A is "leakier" than R12, but you shouldn't loose enough in less than five years or more to cause cooling problems. Causes more problems on converted systems than on OEM, though.

If you have to top up more often, you have a leak and will need to find it.

Dye helps (listen to Larry!), so does an extremely sensitive leak detector (GoMac thermal conductivity type).

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!