With a voltage stabalizer the bulbs last halfway to forever. The other trick is to set the voltage on back of the column to 220 and run the enlarger on 110.

Or buy the original Leitz stabaliser that applies voltage slowly on startup so it take 2/3 sec to reach full brightness. This item cost $400 in 1985 and was $1000 when last made. Good luck finding one. Mine is not for sale.