Re: using tarp under tent in winter necessary?

You can cut the weight considerably from an "official" footprint or tarp by using a self-cut footprint made from a 2 mil plastic dropcloth ($2 in your local hardware store, and only 2 or 3 ounces of weight). But, yes, you can dispense with the footprint or tarp in winter, or anytime for that matter, if you are judicious in your choice of tentsite. In fact, most quality tents are made with a tough enough floor that you really don't need a footprint. Most of the hype about footprints is to sell you "YAPA" (Yet Another Profitable Accessory), making the store and manufacturer more money. It maybe costs $3 to $4 for the material, labor, packaging, and shipping for what they sell you for $30 to $50 ("custom fit to your tent", plus it has the official logo). I have used the dropcloth approach for over 30 years, and still have most of the tents I ever owned (they deteriorate mostly from the UV they get exposed to at the high altitudes I mostly camp in, with only a couple tents ever having had floor failures).

It is true that you should take care of your tent - plan where you pitch it, clean and dry it thoroughly when you get home, and avoid exposing it to the sun as much as possible (which doesn't work for me at the usual altitudes above 10,000 or 15,000 feet). It doesn't take much effort to avoid poking it with sticks or walking in the tent in crampons.

In short, don't worry so much about it.