You may have spent a while creating your ad-hoc report to ensure all columns and filters are applied correctly. It may then be the case that you need a very similar report in which case you can simply copy the report.
As you create an ad-hoc report their is an option after you have selected > create ad-hoc report to "import configuration from existing report". This will then pull through your previous configuration.
When you do this you will be given an option whether you want a slave or self contained copy. I thought it may be useful to outline the difference to help you decide which option to choose:
Slave copy – when a slave copy is produced the columns cannot be changed, they are greyed out. The filters can still be changed.
Self contained copy – means you can edit the columns and filters