Is it time to change spark plugs?

[His Dudeness]

There have been plenty of horror stories on here of plugs shearing off when someone's tried to take them out.
I'd consider taking the bike to a dealer and asking them to change the plugs for you. Not something I'd normally recommend for such a simple job, but if they've been in there for a decade or so, they might not want to come out without a fight.

Good idea. I take mine out every few months to stop them getting stuck