All things are compromise..

I haven't gone though the first set yet, so can't say from experience.

Surefire says the L4 puts out full (regulated) light for an hour, followed by 1.5 hours of declining light. Their estimates tend to be conservative (very conservative, compared to other manufacturers). That doesn't sound great, but there are some mitigating factors:

Cells tend to actually last longer (in total "on" time) with intermittent use than with constant use, and that's how they tend to be used in the real world.

The lithium cells (CR123) are now much less expensive ($1 - $1.25 on-line) and are very lightweight, so it's no trouble to carry a spare set or two (do NOT buy them in a store, where they range from $5-7 EACH).

I've already ordered a "McGizmo" 2-stage switch for the L4, which should provide me with about 8-10 hours of lower level light. This is helpful anyway, as the stock L4 is too bright for many common tasks.

There is always the L2- which is an inch longer, almost the same price, but comes with a 2-stage switch. Surefire says it lasts the same hour on full-out high (which is listed as brighter than the L4), but an amazing 18 hours at the lower setting, which I understand is still pretty bright, and adequate for routine use.

Another option, of course, is to carry a small, lightweight, low-power but long-lasting LED light for prolonged use where you don't need the bright light. The Inova X5, for example, isn't all that much smaller, and not nearly as bright, but it does have a reputation for sucking the last bit of energy (and hours of use) out of the same lithium cells that are already drained too far to be useful in the more powerful lights.