I love mine. I don't really uses it more then 20 times a year. I mean, I might vacuum seal up 10 or 12 items on some of those times. I've probably did maybe 300 total vacuum seals ( it's a shame they don't have a counter ). I've never changed the oil on mine yet. I probably should, but when I look in the window it still looks clear and still pretty much at the level it was when I filled it.
I honestly don't know how often you should change it, but I do know I'd be wise to change mine soon.
When I bought mine, I got a pretty good deal, but still wasn't cheap. I looked at the prices recently, and now I'm very glad I bought mine when I did.
10x13" in theory is the max bag size, and I can tell you that realistically, you can't get more than about 10" long hunk of ribs in that size bag.
I almost bought a used VP320, for about the same price as I paid for the VP215. I was like 30 minutes from getting in my car and driving 4 hours to Chicago to pick it up, when I realized the VP320 weights nearly 200 pounds, and I decided there was no way I would be able to move the thing by myself. VP215 is hard enough to move ( so it doesn't get moved , or hasn't in the 2 or 3 years I've owned it).
I have absolutely no regrets about buying mine.