Welcome to Club Lexus Ajjk!
You don't specify whether you have HID headlights or halogen headlights. HID headlights should last 5-7 years (depending on use) before going out (or losing enough output that they should be replaced). I don't remember how long exactly halogen bulbs seem to last (I went to HID and never looked back), but I would guess somewhere around 5 years, depending on use.
What do you mean by it's usually a different light? Do you mean that 1 taillight will go out, and then 6 months later another taillight (or parking light bulb) will go out? If this is the case, this may actually be normal. Let's do a thought experiment.
So for example, in the case of the taillights, there are 4 bulbs. So say you replace the driver left one today, 6-9 months later the driver right goes, 6-9 months after that the passenger left goes out, 6-9 months after that the passenger right goes out. 6-9 months after that the driver left goes out again. So if you do the math, the first bulb you replaced, the driver left side, lasted you 24-36 months, which is 2-3 years. Add a couple more bulbs to the mix (which are also on when the taillights are on), such as the front parking lights (2 bulbs) and front side marker lights (2 bulbs), and now you are looking at 48-72 months (4-6 years) since the last time the driver side left taillight burned out. 4-6 years of use before burning out seems perfectly reasonable to me.
If this is what is happening to you, you might just want to spend the money and replace all running light bulbs at once so you are good for a while.