If you do it at all, it is very likely that your account will get reset. No real way of knowing how long.

Just a suggestion, don't cheat. Play the game the right way. If you really have to have a high rank profile, just create a local gamertag and just use that to mess around in Forge for hours at a time. If it isn't a Live account, then there shouldn't be a limit to the credits you get from something like Forging.

Within a matter of hours usually.

Your credits reset and you will be demoted to recruit

your commendations stay the same to further a big "f*uck you" with love from bungie you maybe banned for 2 weeks as well and if you complain to them they will double for ban time cheers