1. imho, the gas station audits should have a base fee of $25 per location plus any reimbursements.
2. You will become efficient over time and as a result of that you may begin to disagree with #1 above.
3. People who do these as routes work with schedulers, factor in travel, lodging, ease of including work or necessity of excluding it, etc.
4. I encourage you to try a few, find your way or your system, and think about routes.
Bach is not noise, Madam. (Robert, in Two's Company)