That's one option.

I found that when I switched from an old Graflarger back to a new Aristo D2 High output head, which has a heater to keep the tube at a more stable termperature, I got much more reliable results.

Another option is to use a compensating timer with a probe that measures light output and adjusts the time accordingly, like the Metrolux timer available from Calumet. If I find myself using the Graflarger again, I'm going to get one of these.