The idea of usability as something optional and only applicable in latest stages of the development process is obsolete. Usability is very valuable for users, reason why counting with proper tools for assessing usability in products like touchscreen-based mobile devices is needed. One traditional usability evaluation method is the heuristic evaluation, where evaluators through the use of usability heuristics detect usability issues. In this paper we introduce a revised version of our previously proposed set of 12 usability heuristics for touchscreen-based mobile devices. Three types of validation experiments were performed: inquiry tests, heuristic evaluations and experts' opinion. Results supported and checked the utility of the proposal.