In general, you're going to have to balance between:
(1) How much you're working (total shifts + length of shifts),
(2) How much flexibility you have,
(3) How busy those shifts are / how much support you have, and
(4) How much you're getting paid.
So if you're working 10 shifts a month, there's probably a "catch" in that there's probably one or more of the following:
(1) long shifts
(2) concentrated on weekends or less flexibility with dates (which can be tough if the rest of your family is on a normal, M-F schedule)
(3) busy with a lot of coverage / admitting / only person in the hospital for codes / RRTs without resident or mid-level support
(4) lower pay
I suppose if there's a job that makes you only do 10 easy shifts where you're sleeping the whole night, lets you choose and move around shifts easily, pays you well and has a bunch of support, then of course that's great...but your job may not be super satisfying and it's only a matter of time before they realize that you're expendable / getting paid too much =)
I worked as a nocturnist before applying for fellowship -- fewer shifts a month than chessknt87 above and I had an overall good situation at work (but also safe to say I likely got paid less), but I would still say it would have been hard for me to do long-term just because it can be tough to not be home at night or for dinner ~half the month if your family is on a normal M-F schedule.