Root Beer Question - 1st Timer

Made my first batch of root beer last weekend using Cooks Root Beer Extract and some Ale Yeast (just did a 2 liter batch). Had it sitting at room temp for 2 days (between 68-72 degrees) at which point the 2 liter bottle was very hard so I put the bottle in the fridge and we cracked it open tonight........tasted pretty flat so I am thinking I should have left out longer before moving to fridge. How long can I leave this out at these temps without fearing it may explode? Just not sure what the optimum times/temps are for the different stages with soda. I decided to make a cream soda last night using similar methods / same yeast and have similar questions.....how long should I leave this out? Is a max room temp of 72 too cool? When should I move to fridge and how long should it sit there. Have googled these questions but gotten no consistent answers so hoping I can get some good advice here. Thanks in advance.

--One final question.......so the directions I used for my batch called for cold water but I have seen a lot of recipes online for rootbeer that say to use warm water..........I was actually surprised at cold water but went ahead and followed those instructions but that said seems like it would have caused the ale yeast to not flourish.

It's hard to give consistent answers to these questions because there is no consistency to it. Even if you thoroughly mix the yeast and have several bottles of soda, it won't even be consistent from one bottle to the next all the time. Certainly not from one batch to the next.

I'll share my experience for comparison.

I just did my first soda brew as well (though been doing assistant duty for my roommate in beer brewing for a few years), and the yeast did not react like I thought it would at all. They were stored in the same temperature range, with should have been good for the ale yeast I bought. I was told that with using these plastic bottles, it was best to squeeze one of them in a bit, and when it popped out that I should be about ready on the carbonation level. At day 2, the bottles had not moved hardly at all. I opened one bottle (I made six 20-oz bottles worth) for testing on that second day and it was not that great. I gave the remaining bottles a quick shake and let them continue on their way. Overnight (so at about 56 hours), the yeast went nuts and they all were mildly carbonated with the bottles popped out. Into the fridge, and now I wish I had given them another 8 to 12 hours. It's not too bad though.

We had used that particular brand/strain of ale yeast before, and it had always been rather aggressive. I'm not sure what changed in it. For beer, the temperature was right for the yeast. I'm not sure why soda would be any different. For most ale yeast you should be able to get away with 60F to 90F, though the extremes are not ideal. You usually want to shoot for 70-75F. Check with your homebrew supplier and ask them about a particular yeast you are buying. Hopefully, they can give you a better idea of how the yeast reacts. As was said, typical results are not always guaranteed though.