The current date limit for the phasing timeline is 2029 and there isn't a way to extend that at this time. Since timing isn't important in your case, shortening the time span for the phases would be the best option.
Unfortunately, there is no way to change the default length of a new phase, and there isn't a way to multi-select and shorten multiple phases at once.
This does sound like it would be a very useful quality of life feature to have, though. I recommend submitting this idea on our public roadmap here, so our developers can review it and consider adding this to our development backlog for a future update.