What do you do with objects in the game that seem useless or bore you now that you have seen what they do?
How do you use these objects to bring back the "fun" in them?

For example I have played with the the genie lamp (AL) and the lemonade stand (OFB) but now I am bored with them. Any ideas?

Just don't use them? or don't use them too often, so that they will not get so boring.

Assign rules for their use. They won't grow stale because you don't use them all the time and simply qualifying to use them becomes a mini-goal.

Do the same thing most people do in their homes and bury it in a closet or on a shelf to collect dust. Some day in the future when you are reminiscing about "the good old days" you will take it out and play with it again. I have a lot of stuff for my sims tucked away in their inventories. It's usually stuff that I find irritating to hear over and over. Like the pinball machines. I go through a lot of time finding stuff for my sims to do, so I find it annoying when they obsess over one object, especially noisy objects that make them lazy or make them whine because they didn't take care of other needs while playing/using that object.

Sometimes stuff in their inventories disappears forever. It's kind of like a garage sale. If my sim has a game or furniture in their inventories, I consider it community property, so another family might get it when they come to visit. Some stuff has been all over the neighborhood. While some things, like fish and produce in the inventories really help out my new and poor sims. I especially like it when my wealthy sims are in the "Welcome Wagon" for sims new to the neighborhood, because I buy stuff with their "excess" money to put in the inventory for that occasion. Or when my sims make enough money to upgrade their sofa from the 10 simolean sofa to a mid-range sofa, then a new sim will get their old one.

But it isn't all freebies or handouts. Some townies that moved in had stuff that didn't fit the household they moved into, so it gets passed along to a household that could use it. A bunch of love tubs have been stashed away because I just don't like the gaudy-looking things. New sims might get to use one for a while, but I fully expect them to earn the money to get a hot tub I like to look at. And some stuff was really great to get when a townie moved in, like bubble blowers and DJ booths, but the family just didn't have any room for them. And I personally love to rummage through the inventories because I forget most of the contents.

Recently, I moved Laerah Tada into a big house with the Raven sisters and found out just how much I've neglected their inventories because they had great stuff from their previous moves and from other sims moving in and out and Laerah had all the belongings from her two sisters that passed away and her lover Sol. And the Ravens were one of my first and favorite families, so they drank Elixir of Life like it was water while I played them for days and days at a time. They had so many different jobs, so they had acquired most of the career rewards. Combining those households really helped spring clean their stuff. They had about 60 extra counters. Because I didn't know how to use the design tool when I re-decorated.

You don't have to have as many rooms for your house if you have dual-purpose rooms. For my small homes, I may let them have a mahjong table, but then there is no room for the hot tub. So the hot tub goes in inventory for a while. And later, when I'm tired of them going to community lots for the hot tub, I put the mahjong table away. Exercise equipment rarely has a permanent place. Take it out, get a good workout and put it away.

Other than that, there really isn't a magic potion that will bring back enjoyment of an object. Move on to another object, or hang on to the old one until a future day when something inspires you to use it.

Thank you cheshirekat, this part of your reply gave me some ideas which was the point of this topic.