It is always a hard choice to make, when to stop making repairs on the leaking roof and replace it completely. The easiest place to begin from would be to consider whether the roof repairman has almost made residence in your house for the number of times he has to come. You can only repair an old and aging roof for so long before duty demands that you actually replace it. If you realize that you roof is so old that its beginning to split for being brittle, you can be sure that no amount of repair work will finally cure it. When you get to this point, you only need to consider doing some small scale repairs as you plan on replacing the roof completely.
There is a problem with indecisiveness and waiting for too long where your roof is concerned due to the damage that can occur to other parts of the building. There have been situations where homeowners have tried to postpone the decision to replace the roofs of their houses thinking they are going to save money only to realize they end up replacing more than the roof at the end of the day. Taking too long to decide whether to repair a roof that is already falling off will cause damage to the entire roof structure of the house including steel deck and this end up making the entire building unsafe. Failing to act at the right time will end up costing you several times the amount you should have spent replacing the roof if you had acted earlier.
The best thing to do when you are in doubt is to consult a roofing contractor or an engineer to advice you on what your safe options are. This way you will be able to determine early enough based on the viability and costing whether it is time to go one way or the other. A simple formula for determining what to do is to take the amount of money it would cost to replace the roof and divide that amount with the number of years the new roof is likely to last. If the answer you get is almost equal to or less than the amount of money you will spend in doing repairs, it may be time to get a new roof. Your roofing consultant should be able to show you the best way to go about doing the replacement and small repairs as you wait to begin.
If you make up your mind in good time to do some long term repairs sooner rather than later, you can push your roof a little bit further and save some monies as well. The secret is for you to be always vigilant and be on the lookout for small problems that can eventually become bigger if they are not addressed at once; they have a tendency of becoming bigger and more expensive to deal with later on. You should always have a plan for respecting your roof every once in a while and do any repairs that surface while they are still small. Waiting until you see a leak could be waiting for trouble, safety lies in knowing when to take action.