I forget the limit of timers, but you need to understand that you can max out the memory will before you reach the timer limit because there is a limit to the number of events you have in memory. I think the event limit is around 380, I'm not sure, but that limit can be reached long before the limit of timers. Each instance that a show airs, repeats or new, is added to the memory of events. While many of those events won't record, it still takes up memory.
For example, let's say you want to record a show like Modern Marvels on History. Well, that show airs something like 35 times in a week (at least it used to). Now, someone in your household want to record MTV shows like The Real World, etc. Some of those shows will air as many 40+ in a week. Add another MTV show for another 25 or 30. There are a lot of kids shows that air like 50+ times in a week. We have only used a few timers, but it won't take but a few more timers like the ones above to take you to the EVENT limit of some 380+. When you reach that limit, no more timers are permitted. So, you could have as few as 9 timers, but reached your EVENT limit and the box won't let you make any more timers as it will display the "Maximum number of "timers." But it is really the number of events limit that you hit.
It is important to note that as time occurs for each event, it will then purge form memory and now you have more events available. So, let's say MTV airs their Real World marathon and Made marathon on the same day taking up 50 EVENTS. Well by the end of that day and the time for the events pass, you will have 50 events cleared and will now be able to make new timers.
That is just one example just to illustrate a point. I hope I explained it clearly enough. And, yes, people have (including me) have hit the event limit long before the timer limit.
The way to see how many event you really have, go to your Daily Schedule and look at the number of events at the bottom, but make certain you "view skipped" because that is the real number. If it is set to Hide Skip, than only the timers that will fire are counted and you will see a lower number of events at the bottom. Then Show Skip, and you will see the real number of events in memory and how close you are to your limit.
I have seen the precise limit numbers for both timers and events posted on here, but I just can't remember them. I hope this was of help.