My experience: Umarex Beretta 92FS, 8 years old.

Used mainly in winter season, so can sit for several months unused.

Never left bulbs in it.

First 7 years I used Umarex bulbs. Never missed a beat. Always a drop of Pellgun on the tip of each bulb.

Easily shoots 2 mag's worth into 1/2' - 3/4" group at 6 metres, unrested. To mix units...

Last season I changed to Crosman bulbs - which appear to have some oil in them. NOT the Walther 'maintenance' bulbs which are for occasional use.

Got gun out a month or so back, bulb in, not working. Opened underlever and CO2 escaped, so bulb WAS pierced. Tried with several bulbs - both Crosman and Umarex. Maybe one bulb in 5 might work, but missed shots occurred.

Valve clearly sticking.

Flushed it, around 300 shots through it, and gun is now 100% reliable again with Umarex bulbs.

So, for me, Crosman bulbs will now be relegated to occasional (maybe 1 in 10) usage...