1980 Suzuki GS450 that is otherwise running well; took it on its first road trip of about 1,200 miles recently.

After getting back, I noticed the oil pressure warning light is taking a lot longer to turn back ON when I kill the engine after running it for a short period of time - i.e. the oil pressure is staying higher for significantly longer (or the bike thinks it is) once the pump stops pumping. It used to go on about two to three seconds after the killswitch was flipped; now it easily takes ten to twenty seconds. The light doesn't take any longer or shorter to turn off when I start the engine.

My concern is that there's something blocking an oil gallery or otherwise restricting flow/volume and causing the pressure to remain high but choking parts of the engine from lubrication. However, it did also drop twenty-ish degrees (from the seventies to the high fifties) here from when I went on the road trip, and so far I've just ran the engine for maybe a minute to check operation, so it could just be the colder weather (not my first winter with a bike, but it is my first winter with this bike).

My question: should I be concerned? If so, what should I do? If not, are there other related symptoms (using or leaking a lot of oil suddenly, etc) I should watch out for that could indicate a problem here? I kinda guess it's the cold weather but this bike's been such a peach that I'd hate to grenade it through something stupid.