Mine varies between high 40's and low 60's.
In terms of getting a good 'behaviour' strength isn't the only factor. The 'cleanliness' of the signal is hugely important, too. Low Bit-Error rates are the key to good behaviour, and you can get low rates from a weak, but very clean signal. Conversely you can get high error rates from strong but dirty signals.
For example, if your Digital signal suffers from the same problem that causes ghosting on analog, then, even if it's strong, you may still get errors.