Personally I would opt for always on bright LED lamps with rechargeable batteries, remember to carry spare batteries or leave an extra charger at work so you can recharge them all the time. I am not a fan of the flashing LED's but as an extra safety measure they would be fine.

I hate regular rechargable batteries. They have the life span of a house fly.
Duracell FTW!

I find good quality modern rechargables often outlast Alkaline cells. My AAs have a capacity of 2500mAhrs and seem to hold their charge for almost a year. I even use them in clocks and smoke alarms now.

Are you sure you're not just using crap old ones?

+1, even older 800s of mine are still going strong

Quite possibly.

Not sure you want to use rechargeable in a smoke/carbon detector. One of the problems with conventional rechargeable batteries is the self discharge – at between 1% and 2% per day this is higher than the drain from the smoke alarm itself.

So a conventional rechargeable will be pretty much flat after just a couple of months or so. This in itself is not such a problem as you can just take it out, recharge it and put it back in.

The real problem is how quickly the voltage drops off as the rechargeable battery approaches exhaustion. In most single use batteries the voltage drops off at a fairly consistent rate, so the low battery warning beep you get in a Smoke alarm can go on for weeks. Rechargeable batteries hold their voltage really well right to the end, but then drop off very quickly, this means you get the low battery warning for a much shorter time – This can be just a day or so, perhaps even just a few hours.

So unless you check your smoke alarm battery ever day, there is a real possibility of the rechargeable battery going flat without you ever knowing! – not a great thought.

I would suggest you use conventional alkaline type batteries or, for extra piece of mind, why not look at using the ULTRALIFE Lithium PP3 type battery; this can last up to 10 years in a Smoke Alarm.

That's simply not my experience with the modern ones. The fast voltage drop off is only really present on higher drain loads, and modern rechargeables really don't self-discharge that much.

They last over a year in my smoke alarm, and then it starts beeping to warn that it's running out. It can easily carry on beeping for over a week, giving plenty of warning.

My smoke alarm is tested every time the wife cooks

I have just bought some sanyo eneloop batteries and they are lasting longer in my wiimotes than duracell gold tops. Can recharge them up to 1000 times too!