Bob,
If they cannot find any leaks, I'd go somewhere else.  My mechanic loaded the system with a dye charge, put it up to pressure and let it sit for a day, then went end-to-end on it with a black light looking for the leak.  They found NONE, so continuing to diagnose the problem they looked at more items, individual components, etc.  Still nothing.   Then they started up the Van, WHAM, there it was, the seal on the compressor itself was leaking but ONLY when engaged!  Needless to say, my leak was less severe than what you appear to have.
Oh, I have a '91 Carat, and I was worried about the hoses as well, but my mechanic, in looking for the leak, found no reason for me to replace these hoses.  As far as I know, they are the originals, so that's a good 14 years (my '91 was built in '90) -- thus, 4 years does sound a bit odd.
I really trust and like this mechanic I use for these types of repairs, he does a good job, charges a fair price and follows up to make sure I'm happy.  Not bad for a 2-man shop.
My repairs were in the $900 range, including $265 for a rebuilt compressor (non-OEM, I'm running R134 now).  My A/C isn't bone chilling on our hot and muggy Florida days, but it is more than adequate to cool the entire Van to a point where I'm comfy.
    -Robert
-----Original Message-----
From: Trooz <trooz@ADELPHIA.NET>
To: vanagon@GERRY.VANAGON.COM
Sent: Thu, 5 Aug 2004 19:33:45 -0700
Subject: Vanagon a/c

Is it reasonable that after only four years I may have to replace the
hose that runs from the compressor to the front of the van? I don't
know the part number or even the correct name *compressor to condenser*
on the invoice, all I know is that it cost me over $400 just for that
hose along with another $1,400 worth of a/c parts and labor four years
ago. Now I'm adding, according to my current mechanic's invoices, about
1 1/2 pounds of Freon every other month and they can't seem to find any
leaks. They say it may be behind the cabinets.
Does this sound reasonable to listees with a/c experience?

Bob Trousdale
'90 Westy