Filaments of those Lumline have stretch coiled and are prone to bend to the point where they touch the support line in between ends. Ultimately, they tend to shorten the filament's life as the resistance decreased...

At least you have a working version

Yeah I wonder what would be the best way to make it work longer...should I use resister or just simply lower voltage by using dimmer?

Either way, it will prolong the bulb's life. However, the dimmer would work the best by running between 60% to 80 % of light output

Way Cool Bulb!...what was the purpose of them anyway?

they look like Fluorescent..but they are Incandescent!...thats Cool!

They were used for under cabinet lighting, and for decorative lighting on counters and dressing room vanities. Here the BELL linear lamps were more common, and are still available as NOS units, though the fixtures are getting hard to find as the poor quality chinese T5 and smaller units take over.