Premiere Pro Computer Question... What's your strategy?

I do a ton of Premiere Pro remote and travel editing, so it's a requirement that I have a high-performance laptop. As anyone in the same situation knows, it's not cheap! Usually I'll spend $5,000.00+ for a really tricked-out top of the line laptop with all the latest components, processors, topped-out RAM, etc and I'll hold onto that computer for about 4 years.  It always seems to be right around that time that the software, video codecs, etc have changed enough that the computer starts to be a bit sluggish.... and that the renders feel like they're taking a little too long for what I feel comfortable with for my clients.

But lately I've been thinking about it... Seems that hardware is developing so quickly that I wonder if it would make more sense to buy a very good laptop for $2,500.00, and then change the cycle so that I am getting a new computer every 2 years. 

Does anyone have any thoughts/experience with this? Better to spend top dollar and get the "best" system every 4 years, or instead get a very good system every 2?  I also wonder what Adobe and the developers would say, if they feel changes in hardware would warrant that it would be better to upgrade every 2 years.

Thanks in advance for any input!  Very curious to hear your thoughts.