My guess is land battles will be longer but it will depend on the number of units involved. The ability of infantry to form squares should prevent the RTW tactic of bringing cavalry around behind engaged infantry and causing them to panic. That, plus the ranged nature of battles and more involved terrain factors should extend the length.
Naval battles I don't know about but this video is a clue.
https://www.youtube.com/watch?v=pxiRP1A0uKU
The battle entailed five ships on each side and appears to be nearing a conclusion after 8 1/2 minutes. There didn't appear to be much tactical maneuvering, just toe to toe fighting for the most part.
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