Never heard of the brand, I'm guessing they are a generic lamp ?
Incorrect cure (all the things you mentioned about) imply the gel & lamp are not matched correctly. It's better to use the lamp recommended by your brand. If your brand says any lamp I would be wary.
With regard specifically to UV, they do have a life span of approx 100 hours and will emit less light as they decline. Bulbs blowing regularly would worry me, they shouldn't blow. It could be substandard bulbs, faulty wiring, etc. I do know some lamps can be temperamental when used with an extension lead.
Bulbs are expensive, replacing them repeatedly is expensive and time consuming quite apart from the unreliability aspect in front of clients.
I think it's time to consider purchasing new lamps, LED is faster, the bulbs are good for thousands of hours, and more reliable. Ensuring of course your product is LED curable and you purchase the correct lamp for your chosen system.