I agree, they are ok for older toddlers, but just bear in mind that the span of time you'll use the wrap depends on how heavy your child is.
Mine is 20 months and 14kg, and I actually have to be very careful of my back because if I carry him at all, in any way, with or without a sling, I get a sore back for a few days.
The ring sling I have does help for very short trips, like getting to and from bus stop, then into taxi, etc, but not if I'm going to the shops. My baby was too big for the ring sling on long trips like that by about 11 months.
I have an Ergo which is more expensive, but has lasted me much longer, and I could take my toddler shopping in that. Still have to watch my back though.
The great thing about Maya wraps and similar is that they have a good resell value, so you can end up getting a good 50% or more back selling it 2nd hand.