The requirement you have is a genuine need. Sadly, UiPaths license regime is way to complicated and confusing. Your requirement would definitely be a tall ask (9 months on 3 months off).
That said, your regional UiPath sales teams has a the right and the mandate to provide you customised licenses, after approval from their central sales team. So I would say this may be possible provided you have a good case.
For example, I know for a fact that, UiPath can arrange a project based licensing type. Say you have a large project running for only 3 months and you need 6 robot licenses. UiPath can arrange a project based robot license for it. It won’t be cheap, but it will be cheaper that 6 robot licenses for a whole year.
Talk to your regional UiPath sales manager and describe your need. Every company wants to serve their customers need. UiPath ideally should do the same.
Your talking of large number of licenses here, music to a sales representative!