The speed rating does not affect a tire's handling - it's about heat dissipation ability, not handling. Don't worry about it unless your wife routinely drives more than 100 MPH.
More important than the weather - what are your wife's driving habits? When conditions are bad, does she really need to go out, or can she wait until things improve? Does she have a long commute, and potentially will get stuck at work in bad weather? Do you have situations where you need to travel long distances in marginal winter conditions? And are you willing to pay to maximize your family's safety in those situations?
Winter tires have softer rubber compounds, that's part of what makes them stick to ice. They all wear faster - that's just the way it is. Here in New England, my family tends to get about 3 winters out of a set, driving them December through March - that's maybe 18,000 miles. That's not wearing out prematurely, it's just the nature of the beast.
I have always put snows on all my family's cars. Tried not doing it once, and my daughter had a accident on a slippery day - partly her fault, but winter tires would have helped. And we tend to drive long distances to go skiing, pretty much no matter what the conditions. So it's worth it for us, but your situation may be different.
One other bonus is that winter tires are outstanding in the rain - excellent grip compared to even the best all-season or summer.
Flymo
