It’s not just Google, you’ll get a mixed pile of treasure and trash right here on BikeForums, too. That’s just how humans are.

The tubeless bicycle tech situation is particularly rife with confusion, but you did receive the answers to your question: all bicycle tires are more air permeable than car and equipment tires, which allows the sealant to evaporate, and bike sealant is formulated differently than Slime and evaporates faster.

The reason those things are true is to due with weight and keeping bikes light. Thin tire casings of lightweight materials and thin applications of tread and sidewall rubber allow tires to be springy and cushion the ride. Sealant was developed for sports applications, so had to be light, and also to coat the inside of a tire to provide air sealing, so had to be liquid and soupy to do that, and could not be a thick gel like Slime (which is not intended to provide air tightness, just puncture sealing.)

As for the sealant refresh interval, it really depends on the tire construction, sealant formulation, and climate conditions. Some tubeless tires are very permeable and allow sealant to evaporate quickly, but some have a thin butyl rubber lining which provides air tightness reducing the evaporative rate. Add in hot, dry climates and things dry faster. If the bikes are ridden a lot, especially permeable tires, the sealant gets used up faster as casing deformation creates little tears and holes which need filled; this is the experience of sealant weeping through sidewalls, for example.

If you want a tire with a longer refresh interval— which I’ve experienced can be as long as 9 months— get a tire specifically designated as tubeless, as opposed to tubeless ready (TLR). The difference there has been (though not a legally defined matter, as I understand it) is that tubeless are bityl lined whereas TLR require sealant for air tightness. For example, see the difference between Schwalbe’s One Tubless and their Pro One TLE (uh, yeah, they use “tubeless easy” to denote required use of sealant rather than “tubeless ready,” just to confuse things!) IRC do the same, with Formula Pro Tubeless (in X-Guard and RBCC models) and Formula Pro TLR (S-Light HL model.)

IRC probably do a better job of explaining the difference than Schwalbe, so here’s a link to their road tire page: https://ircbike.com/pages/formula-pro