Speaker Cable Lengths - W/ Monos

I'm considering having the manufacturer of my 10 foot cables cut the cables in half and re-terminate them for use with my Monoblocks in a Bi-wire configuration. They are very expensive cables, however, and I'd hate to cut myself short on cable (while also ruining their resale). At the same time, I'd hate to double up the longer length due to costs if I can help it.

My short term listening room will work easily with 4 1/2 to 5 foot cables, however, I'm not sure about a future room I'm planning.

What are typical cable lengths for those of you running monos out there? Is five feet usually enough? How far away from my speakers should my 150 lb. monos be?

Thanks in advance for any assistance.