Mark -
Before I start please forgive me but I have allowed my ESP License to expire and I'm not quite sure what you are trying to do.
If you could provide some context that would help.

Yeah you have reached the limits of the timer interval and what it was intended for. What you are asking could possibly be done with programing but I see that you are currently at the Beginner level and it may be outside of your skill / knowledge set.

The search above in the header will help you LOTS in the future.  
Here are two links I found that might help you:
Reminder Date:  https://599cd.com/blog/display-article.asp?ID=1529
Followup Dates:   https://599cd.com/blog/display-article.asp?ID=1445

Thanks Scott I will give that a look, yes Im only starting in access and struggerling some what lol

Mark
My advice is watch the video with out doing anything except make some notes.  Then watch the video pausing as needed to actually do the database as Richard is teaching it.
Try not to jump ahead - it will come eventually.  I've taken all the classes - Beginner to the current developer and there are still things I struggle with.  The beauty of the videos is I can go back and re-watch over and over if needed until I get it.
I'm amazed and the little things I missed when watching it before.  Ask questions if you don't understand.
Just persevere - you'll get there eventually.

Do you want a single timer to run for 90 days? If that's the case, you'll need to reset it. I would recommend having multiple fields for seconds, minutes, hours, days, and then set a 1 second timer. Every second, increment the seconds field. Every 60 seconds, increment minutes. And so on.

Hi Richard, sorry but how would I do that? Im still learning and thanks for all your advice.

This is going to involve some VBA programming. No way around it. I see you're a Beginner user. Like the saying says, you've gotta learn to walk before you can run. When you get to the Developer level, let me know and I'll be happy to record a lesson on exactly this, but there's a lot you need to know before that. Here are some other videos that might help you in the mean time: Flashing Text, Reminder Popup, Reminder Popup Date.

Thanks Richard Ill take a look and go through some more of your lessons.

Access Developer 6 also covers the Timer event in more detail.