I know it can vary massively, but roughly what age would you say children stop sucking/mouthing resources?

I don't think it is teething related with this particular little one, but they constantly seem to be sucking on something. I have a couple of easy washable teething rings that I give them if they are sucking something that I really don't want them to suck, but it is pretty constant. Little one is very settled and happy, so not desperately trying to seek comfort.