Mash Temperature Management

I am trying small batch whole-grain brewing but can't seem to control my temperature during the mash. If it's varying between 140 & 180 degree F, should I be letting it mash longer than 60 mins? And which is worse, too low or too high?

Are you using electric? If so yeah you kinda got to watch it,it will surge sometimes but you just stir it and recheck it and usually will go back down to normal.If you wernt watching it and it was stayin at 180 then pull it off and add some cold water and stir. Too low is probably better but you will need to mash longer most likely.
If this is a problem and bothers you you can always get to your mash temp then wrap it in blankets/sleeping bag/fleece or anything insulating and leave it for an hour,it shouldnt drop more than a few degrees.

Yea, get it to the high side of your mash temp, maybe one or two d egree's hotter...then take it off, put the lid on and wrap the hell out of it in blankets/towels/sleeping bags like he said...

You can also buy thermoprotective type wrap at home depot and rig together a holder for a few bucks probably...

Too high is worse because above 170ish the grains will stop converting sugars as well or at all and start to give you weird astringent flavors.

Agree with both of the above. I brew in a bag, so I mash in the kettle, on my stovetop. When I want a very efficient mash I usually start at 158°F and just let it drop for 60-90min till it gets to around 144°F. Works great for me. If you let it get above 170°, you're in danger of denaturing the enzymes and not being able to convert any of the starches to fermentable sugars. If you leave it below 140°, the enzymes will just sit there and not do anything. As long as it's between 145°-158°F for 20min or so, you should be good. Check that hydrometer. And as always, RDWHAHB. Cheers.

If possible set your oven on at 150 and then set your pot in there after you hit your mash temp. Trying to control a small mass temp is dang tough in my book.

I've had the best luck just turning the heat off and putting on the lid and letting it be. it climbs a couple degrees and then drops about four. It sure beats messing with the heat and it is very consistent and repeatable. The oven will make the temperature climb if you can't get it to stop at 150. Also I've found that picking up a kettle with 10 pounds of grain and 4 gallons of water and trying to put that in the oven is more difficult than ranging a turkey out of the oven on thanksgiving.