I am really surprised to hear such low temps?? When I started a couple years ago I saw some side by side studies and 84 to 86 degrees seemed to be the sweet spot and it offered a nice range to drop ten degrees for fruiting because 74 and 76 are easy temps to maintain in fruiting... I have colonized at room temps (ranging 66 to 74) and when I incubate I get much faster colonization and I also think the mycellium is more vigorous and thick.
I had a grow room set up with 50 plants and two martha green houses so for a while I stopped using an incubator and starting using a box to keep them dark and the heat of the grow room to incubate them.. my results staggered. An incubator definitely is worth it and its a tiny extra step.
A big part about incubating for me, isn't just the jars for spawn, but also the trays after I have added sub and cased. I put them back into the incubator and that has really stopped contams too and I think its in part because of how vigorous the mycellium grows with a solid source of heat.
I am just now beginning to grow again after we moved into a new house. I had to take it all down for the move a couple months before we moved and now I have just now started emptying the storage unit out of my equipment. I am half tempted to order another aquarium heater and do a side by side again... although I feel like pc'ing all those jars would be the hard part lol have to run my pc four times to fill up two incys
There are a lot of options for mushrooms. If you are willing to spend the extra ten minutes and the extra twenty bucks an incubator is def worth it. Just remember that to fruit mushrooms want temps to drop. So if you incubate them at room temp you should have your fruiting chamber just a bit cooler than your room temps. I feel like it is easier to heat a process than cool a process... so instead of cooling the ten degrees into my fruiting champer I add the ten degrees during incubation so when they come out they get the temp drop they want. Its really all about fruiting. And, fruiting is really all about a drop in temp. However you chose to go about getting that temp difference between colonization and fruiting is really up to you because there are 239478329 options but an incubator gives you that temp control in a cheap way.