A/C Recharge Question

[Decolliber]

Last June I had my a/c checked for leaks and recharged, after installing a new rear condensor and receiver/dryer. I just had it recharged again this morning, one year later. The tech said it had lost about one pound of R12. Total capacity is 48 oz. Is loss of one third capacity over a year a reasonable rate of loss?
How often do the rest of you have to recharge?

[Boss]

My 87 loses about the same amount per year with no detectable leakage points. My understanding is that this is due to the permiability of the stock (non-barrier type) hoses.