My first laptop lasted 6.5 years, but barely. I think it was poorly built, the heat became intense enough to ruin the keyboard. I still use it occasionally with an extra keyboard.

My current laptop is 3.5 years, and as good as new.

I think if you want your laptop to last awhile, you need to futureproof it some ways. While all these updates for various browsers/ OS/ etc. are designed to work for all computers, they work best for higher spec computers.

Don't buy this, or any 16" from 2019 onwards. They all throttle like nuts and are just terrible, trust me and every other user on forums. Wait for the M1X 16" pro like I am, cannot wait flog this POS.

Sounds like you have either thermal issues (thermal paste degradation, fans, dust build-up, general dirtiness) or it's time to replace your hard drive (or both). It also could be something more trivial, like too many installed/running applications or some spyware which could take a lot of your system resources. I'd rebuild the OS first (fresh install) before moving on to hardware. And if you have the old mechanical drive, do yourself a favour and replace it with an SSD ASAP (when you said "defragmentation" I assumed you have one). You'd be surprised on how much of a bottleneck the old HDD can be. My laptop is also 5 years old, and it went through a little restoration a few months ago. For less than $200 and one working day, I made it feel like a brand new one. It takes only one bottleneck to make your whole system feel like a piece of crap.

my laptop has 5 years

one time in three months

clean up ( open and remove all the dust)

defrag

it's slower but runs everything yet. 

I changed the normal storage to an SSD.

it's a gaming laptop with an old Geforce 980M, runs ok

They don’t. I have one, from december 2019, the mid-range 16” model which has an i7. Best computer I ever had.

Yeah they do, especially the GPU. So common for the FPS to drop significantly after a while as the clock speeds nose dive to keep cool. Like all MacBooks post 2013, technically flawed just to look hip and cool.

Countless upon countless users have all the same overheating issues, Apple couldn't be arsed to put competent cooling system in place, but that is normal for them. Explains the obscene number of return and refurbished units they always have on sale.

My old HP DV-6 has lasted since 2012. It runs, slow like shit but I can get it running lol. Did have to replace the battery once as well as the keyboard once. IN that life that I reckon it was on at least 90% of the time. Always on and keeping me warm in winter lol.

My new MSI laptop is pretty cool. Got it late last year. Runs great. But only time will tell how slow it will get.

Well, I never even heard my fans, so there’s that.

Check the temperature during normal use with a program like HWmonitor.

If it gets too hot, do as Captain Yuri says and clean the dust inside, especially the fan and heatsink. Depending on how the laptop is built, to access them you might need separate the heatsink from the CPU. If you do so, then you have to replace the thermal paste (wouldn't hurt to do so anyway if it has been overheating).

Also: Specs?

My father's 600€ 10 year old Vaio is still running fine (1st gen i3, Radeon 5450m). He wasn't going to do any gaming, so I searched for a laptop with a GPU with very low TDP. Don't buy laptops with components that generate heat you won't use.

While watching videos, do you adjust the quality manually? My old laptop has a 768p screen yet Twitch automatically goes for 1080p@60 fps if I let it.

Yes that's completely normal.
I've had many laptops that didn't even come close to 5 years.

My wife bought an $1000 HP laptop that got barely any use and was completely unusable after a few years. It started with frequent blue screens (reinstalling OS didn't help). Then the display refused to turn on and the hinges caused the plastic to break off.

My wife bought during the same time a MacBook Pro which got more use out of it but ultimately also failed after only a few years. Macbook wouldn't charge. (had to buy a new PSU for ~€100). Touchpad wouldn't work anymore. OS would freeze upon loading. reinstalled Mac OS but that didn't fix anything. Even installed Windows on it which at least booted correctly but then showed other kind of issues. Took it completely apart and cleaned it but once more to no avail.

My laptop is used every day for up to 16 hours during weekends or Corona times. Since I know how shitty even big budget laptops can be, I stay with the cheaper options. All the laptops I've bought were between 300 and 350 Euro and I have to replace them every 3-4 years. But I'd rather spent that amount than 1000 Euro which wouldn't last any longer.