A quality canvas tent should require no upkeep other than storing it dry, which means laying it out flat on the driveway when sunny, or in the garage if not.
The absolute number one thing you should be looking for if you choose a canvas tent is the word Sunforger. This is a treatment process that is done in Butler, GA to make the canvas water and mildew resistant. It is important because it is done with minerals, and because of this, does not hurt the cotton fibers that make up the thread that makes up the canvas that makes up your tent. I feel confident telling you that ANY canvas not advertised as Sunforger, is a chemically based treatment (usually done overseas) that damages the canvas and leads to a weaker tent and a shorter lifespan. The best analogy I have is acid wash jeans from two or three decades ago; they did not last as long as your normal Levi's, Wranglers, or Lee's, because the treatment that they went through to look so cool, damaged the material. Sunforger is a bragging point, and companies that use it make a point to let potential customers know. Also, seeing Sunforger is a good way to know that the tent is actually being made in the USA...Canvas Cabins, Bravo Tent, Springbar/Kirkhams, come to mind as some who use Sunforger, and there are a few others that I cannot think of at this moment.
I am the sales manager at Davis Tent, and of course, we use Sunforger. I would genuinely tell you that if you buy a tent made from Sunforger, you are buying a great product regardless of who is making it. Those who are still making wall tents here in the USA have been doing so for at least a decade or two, and I think we all know that in the niche industry of hunting/fishing/outdoor equipment, if you make a poor product you are done in a few years. I would love to have a conversation with you over the phone, and we have some really good specials right now, but at the least, I hope that you heed my advice if going the canvas route and stick with Sunforger so that you do not end up stuck with something that may be worthless in a short time.