Ah, that is a very real issue for now. I haven't had as much of an issue with happening quite that fast, but here's what can help for now:
One thing you could try is to send longer messages. Sometimes we could just reply with "I attack him" or "I run away", but it makes better use of your message limits if you send longer, more detailed messages about what you want to do and it usually gets longer responses from Claude (which makes it take longer to read and allows you to play longer between hitting limits.)
Another thing that can help is sort of 'playing' their system by knowing that the message limits reset every 5 hours. So for instance, if you know you want to play at 6pm, send one message to claude at 2pm. This way the chat will reset at 7pm (5 hours past the first message). So this way you could play from 6pm to 7pm, hit your limit, then continue playing at 7:01 until you hit your limit again.
Otherwise, you can also try continuing with Haiku when the message limit for Sonnet 3.5 is hit. For some roleplays haiku works just fine, but for others it struggles keeping up with all of the plot points and stuff, so it's up to you if you want to try this in your chats.
The only other options I can think of for now are to use chatGPT (but it isn't as good IMO) or to use the Claude API (but this can be a hassle to set up and requires you to pay per message instead of just using the free tier or the monthly subscription)
Sorry if this isn't helpful, I know the message limits can be frustrating. If more people show interest in the game I will consider making a full version that runs outside of claude, but I didn't want people to have to pay as they play so I'm not sure if this will get made. For what it's worth, the people who make Claude promised to try and raise the message limits this year, so I'm hoping they stick to that.