Originally Posted by ItsJustMe
I use NiMH rechargables and just charge them once a week or so. It's not like it's a huge hassle, it's 20 seconds total time (clip the thing off the bike when I get to work and carry it to my desk, throw the batts in the charger, put them back in around noon). So I'm charging them every 4-8 hours of use, out of 20+ hours of expected runtime on the light so it's usually pretty bright.
Batteries in flashers is an application that really calls for non-rechargables. Since the current draw is so low - on the order of tens of hours in flash mode - rechargables don't really make much sense. The NiMH have a pretty serious self discharge of around 30%. Even if you religiously recharge, you aren't going to get the best use out of the battery. An alkaline (or lithium) battery will last for nearly a whole winter riding season even in steady mode (up to 2 hours per day for 4 - 6 months) and perhaps longer for flash mode.
With rechargables, you are more likely to forget to charge the battery and have it fail when you need it. Go for rechargables for high current drain applications, like headlights but use alkaline for low current applications.