Aargh just lost my post! Shortened version! I think the maxi duna multy would be a good upgrade. Another member on here did that with an older hamster who had a tiered cage and it worked well. Our last Syrian had 100cm Barney cage and when he got older and climbing was risky he really appreciated the floor space without the levels. So something like the Barney (without the shelf) or the maxi duna multy would be good. Both are quite futureproof and suitable for a Syrian or dwarf hamster in future.
Our hammy was still quite fast and active on the flat in old age, but I had to set things up carefully so he couldn't climb or fall. The maxi duna would be easy to set up. But they do need overhead cover so they don't feel too exposed. What I did in the Barney was move the shelf right up to roof level so it couldn't be climbed on but could still be sat under. And hung a big hammock across the top which couldn't be reached or chewed but made it feel safe underneath. Large cork logs make good floor toys and overhead cover in a large floorspace cage as well.
I personally think older hamsters adapt better to a cage change as they're more chilled, but it is important to move all the old substrate across (spread it out on top of new as you'll need more in a bigger cage) and to keep the layout similar (eg house and wheel in same position).
This is the maxi duna multy
Cage Maxi Duna Multy
This is the Barney
Barney Pet Cage | Great deals at zooplus!
I think the maxi duna would be a better option for an older hamster as easier to set up and less fall risks, but the Barney is cheaper. I already had the Barney cage for our Syrian. This is how it was set up for him in old age. At this stage I left a couple of things on his house roof and a step up there, because he couldn't hurt himself or fall if he climbed on the house roof, but eventually I removed the step and toys from the house roof.
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