Are you sure you've "never had a problem since"?

How's the cookant level in the rad? Is there ever any air in it?

Does the reservoir level increase, then not go back down?

this happened to a friend of mine about a year ago.  subaru - got towed
home.  huge estimate to fix blown head gaskets.  lost /all/ it's
coolant.  huge mess.  i poked about & noticed a piece of gunge under the
blow-off valve in the radiator cap.  cleaned it out, refilled, and guess
what?  never had a problem since.

so, long story short, yes, your shop was after the $900.  just like the
folk that are happy to sell you a new honda transmission at only 90k
miles because "this one is about to go".  there's countless other
examples.

Is your temp guage staying steady in the proper range?
Are your cooling fan(s) coming on when they should? (force it on by
holding rpm's up a little on the vehicle while stopped in summer
temps.)
Are you not loosing any coolant over time?

if yes to all, you are probably ok.

You can check compression and also check each plug for the proper
color (to make sure you are not burning a little coolant with your
gasoline).  If Ok you should be ok.

I had a vehicle with a blown head gasket was leaking just a very
little coolant into one cylinder.  Actually seemed to run better than
before.  Only clue was the plug would foul every couple of months and
there would be an almost imperceptable slow coolant loss.  If you let
it go, however it will eat up your valve seats on that cylinder head.