I totally agree. Now, the Mercury Vapor bulbs can go closer to a year before being replaced, but that is still with less UVB then when new and they are more expensive, but do give off heat, light and better UVB then but nothing is better then the sun.
Thanks - will get it replaced as soon as I can. He's been outside a lot lately as weather been really good but winters in Scotland are way too cold so good UV light indoors is a must during winter.
I disagree with all of the above. Get a light meter and TEST your bulb. This is especially important if you live in a climate where your tortoise is not going to get much sunshine over the course of a year. You need to make SURE hat your tortoise is getting enough UV at his level. Your bulbs might only last 3 months or they might last 2 years. Either way you need to check them and adjust as needed.
If your tortoise will be getting some sunshine for the next couple of months, I would wait to replace the bulb until fall. That way you've got a fresh bulb for fall and going into winter.