If you’re the kind of runner who thinks a normal marathon makes for a good warm-up before things get serious, you’ll need a watch that has a similar level of stamina – and with a battery that’ll last up to 80 hours in GPS mode, Garmin’s Enduro (from £699.99) certainly fits the bill. Like a lot of other Garmins it measures your VO2 Max, but the Enduro takes altitude and terrain into account to give trail runners a more accurate reading, plus the enhanced ClimbPro mode helps you to pace yourself through all the ups and downs of your route. The Enduro’s 1.4in display is also covered in light-harvesting Power Glass, so you can turn off GPS and switch to smartwatch mode to bump up the battery life to 65 days, or even eke out an entire year in basic watch mode, although that would mean missing out on things such as heart rate tracking, Pulse Ox, and sleep monitoring. The UltraFit nylon keeps the weight down too, but if you really want to shave off the grammes there’s also one made from titanium instead of steel (pictured) that’ll set you back an extra £100. Impossible to put a price on a new PB though, right?