I never thought about it and I am a newbie again.
I am building a 5 servo (non digital) standard 40 class plane.
What mah capacity battery should I be looking at for the receiver?
What I have planned to order is a standard 1500 mah pack.
But before I complete the order, should I be considering something larger?</p>

You will be fine with the 1500mah battery using 5 analog servos.

Digital servos draw quite a bit more current out of your battery as a personal rule of thumb if I'm going to use more than 4 digit servos I do a couple of things to my setups. One I go to 6 volts vs using 4.8 and secondly increase the battery's capacity to the over 2000 mah.

Thanks.
Interesting thought I would have thought that the digitals would draw less.

They draw quite a bunch more. A few years ago 1500 mah was a big pack. I have an outstanding charger I was using for years, still using it too. Problem is batteries got better and better so these days 2000 or 2400 is about the norm. My old charger only goes up to 1500 though. I only mention this because I ended up having to buy a new charger for a lot of my packs. I have a couple packs that are 6v and 4800mah. My normal chargers can't bring them all the way up. Just another little thing to think about.

Yea you'll be fine with that pack.

I used to fly my Avistar (5 servos) on a 1000Mah Nicd pack and would recharge every 4 flights or so. Now I use a 1500Mah 2S lipo thru a regulator and still recharge after 4 flights just as regular maintenance but the increased voltage is sure nice!

OK, thanks, I will just leave my order as it for the 1500 mah pack.

Yeah, you will be fine. I had been using 1200 mah NiMH packs on my planes (5 cell packs) and just recently up'ed that with the new LiFe technology and 1800 mah. I would get, typically, 5 flights out of those 1200 mah packs and I was very conservative about my flying. After 5 flights, the pack would go on a charger.

CGr.