Mother Nature is amazing in the sense that everything she does is to maximize the rewards be it for energy or for synthesis. Humans on the other hand tend to be very wasteful.
The easiest and best money advice I have been given is to use everything to its fullest potential. Next time you want to buy the latest smartphone, DONT if your current phone is fully functional or can be repaired. Same goes with laptops, televisions and clothes. (as long as they do not look too faded and are not torn)
Having said all this, if your laptop is slow and cannot be upgraded, by all means go ahead and buy a new one. Time is money in this day and age, every second wasted counts and makes a difference..