This is why LED replacement bulbs for exit signs (like these for red exit signs or these for green exit signs) have been a big deal -- while they can last 5-10 years, reducing labor costs, they also use less than 5 watts combined, typically paying for themselves just in energy savings within a year.
These LED bulbs are still a great option for those holding on to those older exit signs. But as LED exit signs continue to fall in price (ours start under $20), it's becoming more and more common to replace the older exit fixtures altogether. As our images here show, these range from simple 2-faced signs to edge lit signs to signs with emergency lights built in and more.
An extra advantage to LED exit signs is the fact that they use so little power it doesn't take much of a battery backup to keep them running during a power outage (a standard legal requirement). Because of this, they usually come with this battery backup included. And yes, that's even the case in our lowest cost signs.
So when you're faced with replacing exit sign bulbs, it may be time to consider a fixture upgrade. There's already talk of a future without light bulbs -- where fixtures come with the lighting built in because the lights will last for so many years. Exit signs are one area where this is already taking place, and there are plenty to choose from to fit your design needs.