NOT that you should have to, by any means whatsoever.
The scheduler web interface would only accept a range in the same 24 hr day, if you tried to set it to e.g. start (WiFi off) at 11 pm and stop (WiFi on) at 5 am, it refused with an error (paraphrasing) "end time must be after begin time."
It was ONLY a JavaScript issue. You could trivially bypass it using a developer bar, and it worked perfectly. But they never fixed the JavaScript in all the years I owned it (and I doubt it is fixed right now today).
That thing has been working for almost ten years (granted it is not an office environment), once with openwrt and now with tomato, while rebooting its little and adorable self every night at 3am automatically so that I don't have to.
It's an amazing piece of hardware that makes one say "back in the day".
As to stability, I'd describe it has a mixed bag. I owned one for just under five years and had to do fortnightly restarts (which I eventually automated), and we also owned one at work which needed nightly reboots (DD-WRT provided that).
PS - In fairness to the work one, the building was insanely congested. It was one of these buildings which are shared by three dozens small businesses, and each had 1-2 WiFi networks, plus the local homes also. When you spun up a WiFi analyzer it could not find an empty piece of spectrum, and a lot of routes/APs would crash if you left the "find best frequency" option checked (as they would hop continuously and never find anything).
If I was buying something today, it might be the Asus RT-AC66U (since it is a "compromise" between price/performance).
Digging around I found a thread where customers were wondering what happened to bridge mode and why it had been removed. An obdurate admin informs everyone that D-Link decided it wasn't needed as a feature, so they removed it. The admin is very coarse and ends up locking the thread.
It seems ridiculous that, for a hardware product, a company would decide to remove features in a firmware upgrade. There is a work around, but even if it is a legitimate thing to do, it seems like a terrible product and engineering culture to be this condescending to customers.
Relevant thread: http://forums.dlink.com/index.php?topic=4542.0
End of story: The router ended up going in the trash after other issues, along with two different D-Link models.
It's not the best idea to use consumer grade gear in an office, but then I replaced it (as a temporary fix) with an even older Linksys WRT54GL flashed with DDWRT with no problems.