I guess that only you will know if you can walk/run 60 miles a day for 3 days. If you don't know I guess that the answer is that it is unlikely. Don't underestimate the number of stiles you will have to get over and the time to navigate especially in the dark/rain. Presumably, unless you have someone driving around with food/putting up tents etc, you will be camping as there won't be too many B&Bs that will want to see you. Think about it!
Pennine Way 2005&2014; C2C 2006; SWCP 2007; WHW 2008; GGW 2008; Dales Way 2011; Clev.W 2012; Yorkshire W.W. 2012; Offa's Dyke 2013; Peddars Way & Norfolk Coast Path 2014; Pembrokeshire Coast Path 2015: LEJoG in stages 2018: Camino 5/2019 - 2020 NOTHING!.