Holding a stretch .... really long

I have been following the MS and FS videos.  I find my hips are really still and achy when I do any MS work.  I almost feel like my outer hip gets a cramp.

I was thinking about getting into a periformis stretch and holding it for 5-10 minutes while watching tv.  Is there any issue with holding a stretch like this for an extended period of time?

Probably, because the folks that know recommend 90 seconds each side one time a week.

No problem as long as you keep the intensity low.

Kevin you can stretch all day long if you like, so long as the intensity permits it. Logically if you performed some of the stretch series elements at their intensity anymore than once a week you'd likely cramp up so badly that you'd pull something. Stretching/limbering (think along the lines of like a yoga asana) are good for recovery and help keep the muscle memory fresh so that all the effort of the once weekly stretch series gets a little bit of a boost. I, myself, follow a routine I found elsewhere in some free workout routine (and that I added a few stretches to) but, which basically amounts to the key stretches of all three series:

- Standing Achilles x30"
- Kneeling Achilles x30"
- Vertical Shin x30"
- Front Split x30"
- Standing pancake x30"
- Shoulder straddle pancake (on block) x30"
- Straddle Pancake to each leg (on block) x30"
- Middle Split x30"
- Pike x30"
- Bridge x30"
- Elevated Cat x30" 
- Seated Shoulder Extension x30"
- Shoelace x30"
- Hero x30"

All told, this takes maybe 15-20' and I'll do it either in the morning, right after foundation (before a stretch series) or right before bed. I alao don't these nearly as intensely as the stretch series. Hope this helps. 

There's good points on both sides of things here.  I think the gist is this:  really stretch once per week. limber (not expanding ROM, just stretching at present ROM) daily.  Limbering will not make you sore, stretching will.  So if you sit in pigeon for 5-10 mins, it may be fine if you are propped up on a pillow, but if you are holding yourself up, you will undoubtedly be lowering and furthering ROM during that time, then you will be sore afterwards, and won't be able to stretch and build on that.  This may not apply to advanced stretchers, and there is some work on stretching daily, but in general I would say for most people here that would hinder their progress. Follow the program, be consistent, and you will get there.  Feel free to get the blood flowing and limber daily, just remember, this is not expanding ROM stuff.  I limber almost every night before bed. Keeps the restless legs controlled and relaxes the body.