I did pretty much the same thing... covered the tractor with a tarp with plans of building a more substantial shelter before too long. Using a tarp directly on the tractor has a few drawbacks. In the northeast, it gets wet under the tarp and stays wet. You'll eventually get moisture in your gauges. Also, a tarp covered with snow is difficult to remove from the tractor and, if the snow is heavy enough, the tarp can rip from the weight as you try to remove it.
I searched for fabric shelters for a while. I decided that I wanted one 20' long, 12' wide, 8' high. My tractor with loader attached is 14'. I wanted enough room to leave the rear blade mounted for snow removal, and also some room to work on the tractor if I needed to do that in the rain or snow.
Shelter Logic fabric covers will last a few years. The lifespan seems to depend on how much wind they're subjected to. The covers wear through where they rub on the frame. More wind = more rubbing = more wear. The covers are not difficult to replace, but a new cover can cost as much as you paid for the shelter. Farm Tek makes shelters that will last much longer. Their cover warranties are around 15 years, if I remember correctly. They also cost 3x-4x more. You get what you pay for. You can also order the Farm Tek shelter with more ribs to handle snow load. If I was going to use a fabric shelter for more than a couple of years, I would pay up for the Farm Tek / Clear Span one.
I just happened to come across a Shelter Logic in the dimensions I wanted in the back corner of the local BJs on sale cheap, so I grabbed it! It was worth it and I'm glad I did.
Based on my experience, I would suggest: Checking the door height to make sure that your tractor will fit through it. An 8' high shelter does not have an 8' high door! My ROPS barely cleared the roll up door and I had to hold the rolled up door up with my hand and creep forward as the ROPS passed under it. Also consider getting a shelter that is longer and/or wider than you think you need. Once you have a place that's out of the weather, you start thinking about how many implements you can fit in there, too.
The first winter I had it, it was so great to be able to get to and around the tractor without snow coming over the top of my boots while I struggled with a tarp weighted down by heavy snow.
The second year I had it, I put down a base of crushed stone and hung a string of construction lights along the ceiling rib. It was almost like a garage in there. :thumbsup: Oh, and DEFINITELY get the rear gable vent, even if you have to order it somewhere else. The shelter fabric does not breathe and it will "rain" inside there if there's any humidity at all. The louvered vent stopped that problem completely. That one little vent (12" x 18") makes all the difference.
As was already noted, you have to knock the snow off the top after each storm. That's easy to do from the inside with a flat snow brush. And do make sure to anchor it to the ground. That helps it keep its shape in high winds and prevent it from collapsing.
IMO, the fabric shelters can be a great temporary or longer-term solution if you understand their limitations.