I have worked on small-to-medium RFPs myself, as well as with clients who answer very large ones. What I've found over time is that you're very often going to re-use existing content and assets between tenders, though most companies don't really act on this fact.
One thing I've found very useful is to build a database of RFP responses that is as comprehensive as possible, including information such as the name of the client, their industry, the size of the contract, the services they were looking for, the status (was it a win or a loss?) as well as the contents of the response itself.
This way, when answering a new RFP it's easy to sift through existing ones and retrieve relevant content and information that can be used in your answer. This can significantly cut the time needed to respond to a RFP. It's also an invaluable source of information for new sales hires, helping them get up to speed much faster.