On a 16" bar or so, I like to be able to pull the center up about 3/8" and still be able to spin the chain by hand. If the chain is new, I tighten it on a good bit more because I know it'll stretch. For the home saw user, there's no reason to do that because you can stop and adjust it and pay better attention to it getting slack.
Usually when I fire up the saw, it's WOT until it's out of fuel and I grab another or do a fast refill and keep going. Throwing a chain really slows me down and I usually toss the saw aside and pick up a backup saw. We try to take three identically setup saws to a job for each task (3 climbing saws, 3 limbing saws, 3 log saws, and at least 2 pole saws). It's a great system where you can just throw aside a saw having a problem such as out of fuel, thrown chain, broken parts, not running right, crushed by a tree, etc. until you get to a convenient stopping point or the end of the job and can address the issue without holding up the job or getting frustrated with the saw.
As a homeowner, I'd keep at least one backup saw for that reason as well because you never know when something is going to not work right on your new saw, but I can guarantee it'll be after the equipment store is closed on a holiday weekend with 12' of snow falling on the ground and you have three trees down across the driveway and you need to get out to buy your pregnant wife a jar of pickles or she's going to rip your nuts off for putting that wretched baby in her belly.