The only real way batteries left inside a light would self-discharge faster than if they were left outside is if the light was drawing a tiny amount of power when off. This could occur in lights with electronic switching - microprocessors and logic circuits powered directly, to be ready when the power button is pushed - lights with "always On"/locator features that glow or blink dimly so you can find it in the dark - or lights with less than ideal switches or poorly designed internal constructions that allow a degree of resistance - barely noticeable even with a decent digital ammeter, but enough to drain a cell in up to half the time it should take. Lithium or alkaline, it doesn`t matter - but the inherant shorter shelf life of alkaline cells makes their discharge more noticeable. Coupled with a lesser initial capacity of course.
Temperature has a part to play in self discharge too. Lithium cells are more forgiving of the ambient temperature than alkalines, and will not degrade so much in extremes of heat or cold. Not to say they don`t degrade at all, but the degree of capacity reduction is a lot less.
In an ideal world, a light that is turned Off would draw Zero current, but this is not an ideal world! The two you mention are good lights though and I don`t see that premature draining of cells would become a significant issue in those. You should get your 10 years easilly.
Besides, I`m confident you`ll like them so much when you get them, that you`ll not be able to put them down for long, and will burn the little red cells up in next to no time! That`s the general experience I have
And yes - Lithium batteries don`t leak. The resultant chemicals in used alkaline cells are very corrosive and will eat right through the metal casing if there`s any flaw in its internal coating, but Lithium cells are different and in the years I`ve used them, I`ve never known one to leak ever.
They just give off quite strong, almost sweet- smelling gas....that.....is.......quite........intoxicating..........night-night gas..........