Maybe it is,but I do not think so,though I believe that question has been asked before, fairly recently , which raises an interesting point,that this quest might be bugged.
I think the earlier question raiser didn't get a timely response , and just demolished and rebuilt an infirmary and solved the problem that way.
I was correct here is the link.
Ivar did respond, but looks like the player had done the rebuild as I wrote above.
I only have one now. I don't ressurrect many and with the boosts I can expand it when I'm fighting to heal more. I torched my others and built Manors instead. The silver production is a no big deal to me but the extra boost to training all those mManors make is very welcome.
As with other aspects of the game the number you "need" will depend on how you play.
Graywolf, I'd be interested to know the benefit to you of having five infirmaries. Do you heal and resurrect alot of troops? I am pondering whether to add another infirmary and I just don't know. I have more silver than I can process.
I don't know how long you've been playing but in the later stages of the game its almost impossible to have more Silver than you can process. The Aesir will take MOUNTAINS of it by themselves. Manors also give your troop training a boost which is no small thing.
As far as Infirmaries go..... imo and I'm no expert but have played for more than a year (lvl 34 Palace/lvl 70 hero/all Shamans lvl 60) , as far as I'm concerned ressurrecting troops is a waste of Gold. As I mentioned in my earlier post the troop training buffs from Manors are too good to discount irregardless of your Silver situation.
Firstly, you dont need more than 1 infirmary if resurrecting troops is what you wanna do - Which you shouldnt, unless it is for T1, so you can kill them again and manipulate your trained/loss ratio for traps for example. Or sure, the daily, weekly, monthly quests.
As for how many, i find 2 infirmaries to be the sweet spot. That lets me HEAL nearly 4m troops each time with infirmary expander boost, so thats 40% of a 10m march when doing attacks.. which is more or less the maximum percentages you can get from revive warriors boost.. Healing is cheaper than retraining the same number.
I have 11 infirmary
with current healing gojng as high as 80%
and huge amount of troops in msrches healing is a very cheap way to replace troops
1. Healing is very cheap 24/7, no reason to wait for system bonuses
2. You can heal in battle, which turns 100million troops in to 200m troops equivalent if you heal often.
3. RSS cost to heal is much cheaper
4. allows you to carry lower amounts of troops, hence lower influence but have the same effective power as 2x the troops
example I burned thru 200 million troops the fury but scored over 13 trillion points.
healing is a huge benefit.