I have 600k tavern silver. If I was actually attending to my friends list on a daily basis it'd be at least a million if not 2 or 3 million by now based on what other players who do tend their friend lists have stated they achieve.
So answer: a while. Some could do it for a few months, others close to a year. And this is if they never attend their tavern for additional tavern silver. But those that plunder with a tavern shield in place are probably also going to be maximising on their tavern. Do you really want to potentially give players (both plundered and plunderers) a city shield that can never be countered for a year?
So, you don't even attend to friend list and end up with excessive Tavern Silvers. And you don't think changes have to be made to deal with such excesses? The OP don't even have such excessive amount of Silvers and yet they already think there should be more ways to spend them. Shouldn't players who do have excessive-excessive silvers support this idea?
I'm glad that while you people are talking the talk, others are voting the vote.
So you are not very much into the Tavern, but still try to change the way it functions, without fully knowing how it functions.
Makes perfect sense.
I stand by one of Agent's old comments that "established old players think they've already known everything about the game". Maybe Agent you should apply that to yourself.
I'd like to support the idea with a modification: The same amount of Tavern Silvers as what is requried to active a boost should be spent as the price to deactive that same boost.
Actually, cancel that modification. I support the idea as it is.
+1
For new players, every single piece of Tavern Silver is precious, they anxiously wait for enough amount to expand the table, unlock chairs, replace the "pan"... And they don't have enough Silvers for Extra Turn and have to negotiate the GE quickly, buy extra encounters with medals to fully unitlize the Extra Turn boost, and so on.
But after the tavern seats are maxed out, everyone quickly obtain more Silvers than they can ever spend. Even the previously ridiculously expensive City Shield now in effect costs nothing, silver-wise; it only costs a boost "booth". Sometimes I'm inclined to activate an Extra Turn boost just for negotiation of a single encounter -- not to that extreme but close.
So, this is just a neglected aspect of the game which is out of balance. Changes have to be made but what those changes should be are subject to futher rumination. (On the other hand, this particular aspect has little impact on the core part of the game. The Tavern is just like a mini-game that is maturated.)