Randomly perusing these forums and came across this one. As I am separating 30 Mar 18, I thought I'd shed some light since some of this information is inaccurate. If you are purely separating (not retiring) you can absolutely establish a DOS to avoid a 179. 3-day and 7-day options are for assignments and 365s because they are handled through the assignment process. The separations reg, AFI 36-3207, says absolutely zero about reasons preventing you from separating as it relates to deployment. I'm not even sure the word is in the reg. If you are able to separate given any of the reasons in the reg, you can do it.
In October of 17 I was tasked with a deployment May 18-Dec 18. My UPT commitment ends in March 18. The next day after receiving the tasking, I submitted a separation package in vMPF for Mar 30, 2 days before my AEF window opens. AFPC said it didnt matter and than I could've picked any date before the end of the deployment and I agreed with them, but I'm superstitious and left it that way. My boss knew it was coming because I briefed him of this possibility months ago (because I was also supposed to PCS in the spring and theoretically protected by a DAV code starting in Nov 17). The deployment functional dude wasnt happy, but I showed my boss and the wing/cc the regs and put "completion of active duty service commitment" as my reason for separating and it went right on through. There is nothing in 36-3207 that prevents you from doing this.
Retirements on the other hand, are different. The reg changed a few years ago and now if you can complete your -179 deployment within your ADSC (plus 30 days) you are required to go. However, people get confused about 365, the chart simply says if you are not eligible to 3 or 7 day opt then you have to go on the 365. If you are eligible to 3/7 opt, you can still do that (36-2110). They did also add notes about Stop Loss to the sections discussing retirement and deployments, however.