A grinder has it's place in this deal but 99 percent of the time you can "touch-up" your chains with a file and get right back to work with the saw.
I've been hand sharpening since the 1970's and pretty good at it. My routine is to take 4-5 saws to any outing, cleaned, fueled, razor sharp chains and ready to go. If you hit something or stick it the dirt, or the saw you are using just stops cutting well just grab another and keep working.
I used to touch them up in the field or carry extra chains but these days I will NOT take a saw apart for any reason till back to the shop. It's just a PITA to mess with all that oily sawdust and fiddling with bar nuts and adjustors. Filing without a shop vise can also be a lesson in humility.
Back at the shop after every outing my saws get blown off with compressed air, chains tightened, touched up, bars greased, and saws topped off with fuel and oil. A big shop vise firmly mounted on a heavy duty table is a must for sharpening chains. Make sure they are tight, correct size file, and follow the original angles. It takes some practice but very quickly you will get good at it saving both time and money.
I take the rakers down if/as needed. Used to measure them but these days I just file them couple of strokes and keep moving. I spot-check once in a while to make sure angles and cutting depth is correct. These new chains with the line on the cutting teeth really help to keep you from going too far off course.
Sooner or later you are going to shove the chain into a big piece of sandstone laying on top of the ground, or hit a nail driving in the tree decades ago. Those chains need a grinder in most cases to get them back to even on both sides/angles back to where they should be. You will also get more life out of a chain "touching" it up vs grinding with a machine. They tend to take off more material even when you are pretty good at setting things up.......FWIW.......