I challenge you to today's . On the surface it looks like the absolutely most dreadful, boring, mind numbing set you've ever completed.
When you dig into your weaknesses in technique. Really focus your mind in on exactly what you're doing to improve your body position in the water, your pull through each phase... your mind is engaged and the workout goes much faster.
Technique is the cornerstone to speed in the pool. No way around it.
Check out the link for 2500 and 5000 meter sets.