Thank you everybody.

For now I installed socket extensions, and continue using Philips
DuraMax 50R20. There is definitely more light in the room. I'll see
how it goes with the burnout rate.

I also bought one PAR20, just to try. It does claim much more lumen,
but frankly, I can't see much difference... Maybe it's because it's
shorter, and sits deeper in the fixture, even with the socket
extension? Anyway, for now I am OK with R20, unless they continue burn
out like before.

Thanks again,

Arkadiy