Does the support of the vionic shoe decrease with wear or need replacement

I can't answer for the sneakers. I have several pairs of the slide sandals, that I like and have worn for a couple of years. I do think, that like most shoes, you need to replace them as needed.

I replace my sneakers, if I've been using them for running or hard exercise, every year. One of the pair of vionic sandals that I've worn for 2 maybe 3 summers will be replaced this year. I got my $ out of them and I like the support.

The arch support is built into the shoe. It is not like a piece of foam that flatens so it should maintain the same support for the life of the shoe.

All shoes wear out. I used to wear Beautifeel (excellent support) and after a lot of walking around, I noticed the support was shot. Evenually, you wear down the insole. Nothing lasts forever. I change up my shoes every day, so they can air out, but after a few years of steady wear, it's time for them to go. I can feel it when they are done for.

Not in my experience. The foot bed and arch support in Vionic shoes is very firm - almost hard. Other parts of the shoe will wear out before the arch support will.

The Vionic sneakers all have a removable arch support. That does wear out after a while, as does the sneaker with wear. All athletic shoes need to be replaced after a certain amount of wear time or mileage. Vionic does sell packs of arch supports if you need new ones.

As for the slides and sandals, all of those have constructed bases with the arch support and heel cup molded in. That won't wear out.

All shoes (not just vionics) that have orthotics eventually lose some support. How long eventually is and how much is lost is very individual. I wear my Vionic sneakers and other closed shoes daily and have for almost 2 years (of course, I rotate between about 4 pairs) and I haven't noticed any breakdown.