The oil sucking issue was a big thing with the '08 and newer models. But not isolated to that generation of KLR 650. The 685 kits were developed and being marketed to eliminate oil consumption issues in KLR 650's before the '08 models came out. The first generation KLR 650 has had its share of bad rings, sleeve issues, and controversial solutions.
The point being, you can buy an oil sucker regardless of year. And there is no assurance that conditions won't develop later that were not present when the bike was bought. A change in riding styles and habits when a bike is sold to a new owner may create oil consumption issues. For instance, a rider that rarely exceeded 4800 RPM's may not have experienced excessive oil consumption. The same bike, in the hands of a new owner that flogs it like a rented mule may very well see some oil consumption. A change in oil type, brand and frequency of change may effect oil consumption.
One thing that amazes me is the fear of discussing things with a seller. I would have no hesitation point blank asking the seller about oil burning issues. Presenting a simple question of "If I pull the spark plug, what will it tell me about oil burning issues with this bike"? And see how the seller answers.
I would have no hesitation buying the '08 IF it can be bought for an amount that will allow for a top end job if needed. $400.0 +- will cover that. The upgrades on the '08 are desirable, and you would have a modern technologically advanced bike. Nothing against the '05, but you would be starting with a blank pallet. And bearing the full expense of filling in the "blank". The '08 offers from the factory upgraded brakes, fairing protection, heavier wheel spokes, progressive rear suspension, heavier duty front forks, better visibility due to the new headlight design. Technically, the newer Gen II bikes offer fully transistorized ignition which replaces the analog CDI used before. The more modern unit will better control timing across the rpm range, and, as is usually the case, fewer moving parts means more reliability.
Everything is kept cool by new Denso radiators that are thinner and lighter than before. Kawasaki claims a 20 percent increase in cooling efficiency. A high-capacity 36W alternator powers extra capacity to operate the add-on electronic gadgets touring riders canít live without.
Tell me again what the gain is to hanging on to old technology?