I usually charge on a project basis – we’ll agree a fee for a project before I start, and we’ll only need to revisit that quote if the scope of the project drastically changes.
However, if you need more flexibility in how you use your resource, I can offer you a ‘pool’ of my hours, which you can use on whatever project you need. This can be a one-off thing, or a recurring monthly pool of hours that you use. For more details, get in touch and let’s arrange a time to talk.