First off when you open the globe do not breathe the toxic fluid and make sure you have every window in your home open and or open outside. Also note replacing with the same fluid from same lamp brand does not always work. I've tried a few times replacing fluid using other lamps from the same brand FANTASIA and sometimes they run as they should and sometimes they don't as in they run for about thirty minutes and then the glitter stops moving. I've tried figuring out why with no luck. Not heat related, bulb related and even placed on a timer. Your best bet is to simply enjoy the lamp as it is or pop it open and replace the fluid with fluid and glitter from another glitter lamp. If you save the glitter from the original fluid and rinse it off in hot water you can add to the new fluid you use to replace current. One last thing...if you do open the globe the lamp may not work as it should anymore. There are serious gasses trapped within the vessel and when the globe is opened they escape never to return and impossible to replace. It's all in the chemistry of these tricky liquid lamps. One of the reason I'm such a huge fans of all lamps glitter.
I have successfully topped up two types of fast glitters - Crestworth Living Jewels over here in the UK, and Fantasia Glitter Graphics - using perc, but TLC is dead right - open the windows, wear a mask and gloves, and be very, very careful with this stuff, it is reputed to cause cancer... I use a pipette to dribble the perc in, in small quantities at a time - when you add a squirt you will see the MF swirl and the glitters dance
The UK Crestworth formula is slightly different, I believe, but what evaporates, with Fantasia and LJs, is just the perc element, in my experience, so I've only needed to add this part to the mix.
It's quite a hassle, but so worth it when you get them working properly again - fast glitter is so good!!!
It's not much lower than when it was new. Honestly, I'd keep it like that and enjoy it. It'll still have the same amazing effect.