Well, as a gasman I know a little about grills but not everything. Like everyone Weber makes good/better/and best grills.
If you want to buy a grill that will last you a lifetime buy a stainless steel grill with a cast brass or stainless burner. Many use stamped stainless burners and they aren't that great, cast is the way to go. Even a cast iron burner will last a lifetime with proper maint.
Grill body is also important, you want something that won't rust away in a few years. Cast Aluminum is good, heavy stainless is better.
I have a stainless Bubba's Oven that is about 10 years old, looks and works like it did when it was new.
Next, stay away from fancy features, it's a grill not a commercial range. Electronics don't perform well on grills at this time, maybe one day.
The best grill on the market right now in my opinion is the Wilmington Grill, made in Wilmington NC, it's pricey but worth every penny.
If you don't want to go that route (stainless/stainless) buy the cheapest grill you like, make it cheap cheap, then it won't bother you to throw it away in few years.