Something I've been wondering about but never did test myself yet: do rough service incandescent lamps last longer than standard ones (under normal vibration free conditions)? I know they quote the same standard 1000 hours of lamp life but I'm always wary with that number as it seems to be stamped on anything incandescent no matter what.

Since they do produce less Lumens at the same wattage that would suggest the filament runs cooler which should result in slower filament evaporation and thus longer life. But if they are vacuum "filled" (which, if I got this right, the single coil filament would suggest, right?) that would accelerate evaporation compared to a gas filling so that it would somewhat cancel out the benefit of the cooler filament. But that's just the theory and I'm not even sure I got it right.


So what is you guys experience with rough service lamps, especially in terms of lamp life? Do you know some more facts about them regarding the filament, the filling etc.?

Yes, because of the more filament supports, but at the expense of lumen efficacy.

Rough service per definition does not have to automatically mean longer lifetime, but most makers do design these bulbs with longer life specs as well. The reason being many design modifications are required for either of these features, so it usually gets combined, at least to same extend.

There are actually three branches of such special bulbs, all have many common design features, but a bit different optimization goals:
- Rough service - more robust against damage by external elements (vibration, water,...), but the lifetime could still not be much longer (2..3khours are quite common)
- Long life - just a long average life, does not guarantee less premature failures (the mortality curve could still be rather flat, just the 50% is at longer hours around 8k or so; the 98% point could be still within few 100 hours)
- high reliability - they are designed to have the failure rate low and under tight control within the specified life. It does not automatically mean longer average life (the mortality curve is guaranteed to be above certain level like 98% or so within the rated life, but after that it could fall in rather steep way, so the average life may not be that much longer than the 2..3khour rating)

For American lamps I am not sure, but in Europe it was standard practice to make RS lamps with 1500h lifetime, vs the 1000h of ordinary GLS lamps.

No. The lamp life ratings provided by the manufacturer should be fairly representative of actual life expectancy. Rough service bulbs are much less likely to fail because of rough handling but they will not necessarily burn longer if they are not subjected to rough handling.

Sylvania most recently sold RS lamps rated at 1,000 hours at 120 volts. This is the exception because most modern RS lamps with C-9 filaments are 130 volts and designed for extended life. As a result, these are the most inefficient lamps in general.