Outside light bulbs burning out frequently

Have two exterior fixtures above my garage that burn through bulbs very quickly. Only turn them on a couple times a month for a few hours so only getting 60-70 hours out of them - every 5-6 months, they burn out. The bubs mount bottom side up. They both seem to burn out at the same rate so that rules out a specific fixture being bad. When I replace the bulbs (have replaced them twice), there is no rust on the bulb or fixture socket.

The builder/electrician supplied the original bulbs so I replicated them when I replaced. The bulbs look like a candle flame.

Is this a bulb or fixture problem? I am leaning toward bulb.

Maybe the bulbs I am using are not designed to hang/mount upside down?

The bulbs are a pain to change out due to height (15’ in the air) and fixture design.

Any thoughts/suggestions?

Thanks in advance for the advice!