'86 LX Hatchback, 3.8

My air conditioning went almost overnight from cooling adequately to blowing
hot air.  The clutch was cycling on and off at about two second intervals.
I found that the high side schrader valve was leaking so I took it in to get
a new valve and have it evacuated and recharged.  The shop put dye in so
they could look for leaks in a few days.  It was cooling good, and I took it
back four days later. The mechanic said there was a small leak at the
compressor front seal, but I might be good for the rest of the summer.
About a week later, after not having run the AC for a couple of days, it
started to blow hot again. (I don't mean heater hot, just outside air hot.)
I took it back to the shop and they said the compressor was leaking at the
seams and needed to be replaced.

If the compressor was leaking that bad why didn't the guy say so when he
first checked it?  Maybe the evaporator is leaking.  They said they sprayed
soapy water on the evaporator and observed the runoff under a black light,
but when I bring it to have the compressor replaced they will check the
evaporator with pressure.  Having replaced the heater core I know that it's
a huge job to replace the evaporator.  I also know that there's no way they
could have gotten to the evaporator with water.

I looked at the system with a black light and I do see a small amount of dye
on the seams of the compressor.  As fast as it depressurized I would think
that there would be a lot of dye.  I pressed the schrader valve for a second
and could see a lot of dye there.

My questions:  Could the compressor be leaky enough to lose enough freon to
make it blow hot in a few days and still not show much dye on the seal or
seams?  Could it still have enough freon but something else is causing the
symptoms (hot air and clutch cycling)?

Thanks,

Mr. Bones