NFL Prop bets and middles

[rookie]

What range of middles would you consider value bets @ -120 / -120 ?

Here are my guesses:
Passing yards: 35 ; rushing & receiving yards: 15 . Of course, the exact numbers come into play as well. Say, middle of 200 - 235 passing yd is more valuable than 270-305 one.

Can the prop bettors having a consistent edge give an opinion about this ?

[Justin7]

I'd look around. It's easy to find props at -115/-115, and even -110 if you look around a bit.

[rookie]

-120 / -120 is just the worst case scenario. Yesterday, I had a no-juice 19 passing yd middle (of course it didn't deliver). But, what sort of yard ranges in various categories should be considered for middles (let's say @ -115 / -115 or better) ?

[dwaechte]

It really depends on the total of the number.

[Peep]

I think you first need to find out what percentage of your plays hit in the middle by looking at a whole bunch of games. Once you know that, it is easy to figure out what juice you can afford to pay.