You could use it as a mulch - all the nutrients will have been used up by the growing tomato plants.

Some people reuse it, just adding more fertilizer. I sometimes use it as the bottom layer in a deep planter.

BTD fertiliser and Vitax Q4 fertiliser are the recommended fertilisers to use to rejuvenate composts.
It's not rocket science, but when a manufacturer states enough fertiliser for 6 weeks, you could get the above, mix it with the compost you've just bought and hey presto it'll last 12 weeks.

Just mix it half and half with fresh compost and reuse it. Or mix Growmore into it to replace the spent fertilizer.

Thanks. All very useful.

I wouldn't use growmore as plants require trace elements that growmore doesn't have.
The ones I've mentioned are the best.

I put mine in the compost bin with all the other materials from the kitchen and let the worms do their work and then mix it all together.

Thanks again. Think I'll put it in compost bin as suggested.

Useful info, Scrumpy