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What they can manage as they get older varies a lot from one ham to another & may also depend on any health issues that could develop.
I don't expect to see any signs of ageing until 18months or older generally so you have time to think about it.
Changing the cage completely can be very stressful for them so it's usually better to just rearrange things a bit so everything they need can be on one level within easy reach if need be. If your cage has multiple levels & tubes I'm guessing that may not be possible or the actual floor space may be too small? If so it my be better to change the cage to something more suitable earlier, you could gradually introduce her to a new cage as a play area before moving her over completely.
Which cage do you have? Some photos would help with making suggestions if anything could be changed for the better.