Pete,
I would be happy to work with you on a specific solution; but one way is to create an ongoing project such as Maintenance or Operations. Each task or summary task can be focused on these efforts and your maintenance team can be assigned to the Fixed Duration tasks. When a team member works on the item, they apply their time against the task in PSFT.
Another thought is to apply time at the project, and not task level. You can denote the task or project as CapEx or OpEx.
We are applying the same logic to Admin tasks with the further refinement for some teams to invite all members in as PMs to the single project and teach them to manage their own PTO from assignment to Actuals.
John F. Filicetti, PMP, MBA