I work on a planned six month programme which combines aerobic training with HRM (mostly running and biking), walking with weighted pack, weight training and recreational exercise (climbing, riding, skiing). I've tried a less structured approach in the past, but you quickly get to a plateau, and it's too easy to cop out when you're feeling less motivated. This is really to get me fit for HA mountaineering, and is almost certainly overkill for pottering around in Scotland, but having some basic fitness never hurts.