How long has your husband been fighting the foot problems? If it has been for a while, then I would assume he has been on temp profiles. If he has had profiles, he can go to his PCM at the TMC and ask the Dr. for a permanent profile. That profile will then be forwarded to an approval authority (usually the MEB Dr.). They will look to see if this impacts his performance of his MOS and ability to do basic Soldier stuff. If he can't do that stuff, then he gets put in for MEB and the process will start.
If he has been seen offpost, his civillian Dr. can have a big impact on the decision making process. The Dr. needs to put things in his record that states doing things like ruck marches, wearing combat gear, and bearing weight will cause additional damage, and that his condition won't improve. With this, he can take it to his PCM and help get his perm profile in the system.
As far as timeline, it's not a quick process. As stated before, it could take a year or more. It really depends on the complexity of the case. In my case, I am being boarded for DDD, and right leg pain (sciatica). Those were the two conditions that fail to meet retention standards. All the other little medical conditions I have were not something that would make me unfit were included in my board, but don't get rated by the Army. My board is going to end up being complete in a little over six months. Mine went quick because there was not a lot to look at.
Your husband may very well stay past his ETS date, but I think it is completely worth it. If he is entered in the MEB and found unfit, he will either get severance, or retirement. He also gets fast tracked by the VA. Rather than waiting a couple years to get VA compensation, his VA will be all done by the time he gets out. To me, that is a huge advantage and worth the aggravation off staying a little extra.
What post are you guys on? What MOS? How long has he been fighting the foot problems? How willing is his unit to work with him? How many years in service?