A helpful guide for comparing the output of different event buildings can be found here, using the stats there can help you decide if it's worth holding on to try and upgrade the building with a reno kit or if it's better to replace it with a different event building (if that event is coming up soon). But I also haven't gotten many reno kits, if I had lots of them I'd probably upgrade them rather than remove them. Personally I've started removing some of my event/special buildings just because they don't have any effects that I can't get from regular buildings and they were getting a few ages old. So if you go through a couple of ages you could quickly out do the building and have to ask yourself 'how much longer till that event repeats', if it's too long then you're probably safe to just delete it. Grab any event buildings you can and keep them in storage until you have your city stable and running smoothly. There is the trend for buildings such as the graveyard or confectionery to be involved in 'upgrade quests' where you get the new and improved one but those buildings don't offer anything special. FP production is great to have, but starting out, coins, supplies and goods are more important to you right now.

Also, with your suggestion, if not opening the surprise box till next year and same event appears, what icon difference you need. Are you trying to the collect all event surprise boxes for next few years. After identifying which event, what you are planned to do. After that it really depends on your needs, for example if you are getting lots of coins and never run out you may not need any Kings/Queens. kernbeep said: would identify which event it came from. Obviously the Wishing Well is worth keeping and in my mind so are any event/special buildings that auto-upgrade.

Forge of empires event building box