Always good to hear pilots' real world experiences.

I'll add that most flight manuals warn of spoiler freeze up for both
the reasons cited (mating surfaces and control stiffness) and
recommend ways to mitigate them.

I think this was descibed at length in a thread on the same subject a
year or two ago.

While it's nice to be able to effectively slip a glider (an
increasingly uncommon skill), it's even better if all your controls
work throughout the entire flight. Don't let others lull you into
preflight complacency. Their skills may be greater. I practice no
spoiler approaches regularly (at least a half dozen times a season).
In high performance gliders, I'm only successful about half the time
(that is, I need to pop the spoilers to keep from overshooting). It's
a great excercise, but occasionally humbling.