Thanks. Not sure it's worth it until the very high levels then, and maybe even then. I have the +7, but can't see the incentive to go L3, or upgrade my stonemason past L1 (3-fold increase in maintenance cost for +100HP?). I read the thread on the observatory as well, and cancelled my Guild Hall L3 upgrade afterwards. Seems like an easy call to save these things for the very last, unless I'm missing something, and put the resources to use on walls and weapons instead.
I did it. Easy call for me. When you consider that later academy upgrades for troops like gunners give +2 while adding 100 grog and 2 seconds to each makes blacksmith +2 look pretty good. Especially when you consider it's across the board for all troops. Stonemason is basically useless anyway imo.
I get it, but don't think it's worth it (for me) until after everything else, at least. My average full troop count with the mix I use is around 30, and takes just over half an hour to recruit, so (to geek for a second) assuming a single 75k contribution per day it comes to around 100 gold per unit if I manage 25 attacks per day. I can't play 12-13 hours per day. With the equivalent amount of grog for the +2 upgrade in the academy, two weeks' worth of contributions makes it permanent. Once everything is maxed out and "income" is disposable then sure - why not go for anything that gives an edge. Or if there's nothing else to spend gold on.
I am fairly certain it is not cumulative, for the money it should be! That is a good question for @Chris [Midoki] though