a/c leaks out in about a week

hello, my a/c leaks out in about a week car is 98 4.3 213000 miles is it safe to say the compressure could be bad? i added leak ck and i don't see any thing, but my copressure does look very oily at the bottom of it, i went to the car wash and cleaned it up real good and added more leak ck
are the compressers a weak link? thanks glen

one last thing advanced auto has like 7 or 8 compressers what one can i get?
http://www.partsamerica.com/ProductList.aspx?PartType=387&PTSet=A&SearchFor=A%2FC%20Compressor%20w%2FClutch

The sure sign of a a/c leak is an oily residue.
No, I dont think its a common thing for the compressor to leak.
The best way to get the right compressor is to take the truck with you, then compare the new with the old. Make sure all the mounting bolt holes are in the same location, the wiring is in the same location, and the hoses are in the same location. Also check the hoses to make sure both compressors have the same input and output sides of the compressor.

It's not real common anymore with todays compressors to leak. But there is a shaft seal right up front that can leak and it may be less expensive to have the compressor shaft seal checked and replaced if nesessary than to replace the whole compressor.