Top cases have been losing favour for a while, no idea why. Mine never leaves the bike.
I have an oem tank bag for my Tenere, I've never even put it on the bike. Between the top case, panniers, and two 30L dry bags when camping, I don't need any more space.
Current: '15 Tenere ES - 30k km
Past : '06 FZ6 - 115k km, '06 KTM 625 SMC - 30k km, '06 V-Strom 650 - 80k km, '07 FZ1 - 70k km
Instant information is instantly obsolete. Only the most banal ideas can successfully cross great distances at the speed of light. And anything that travels very far very fast is scarcely worth transporting, especially the tourist. - Ted Simon, Jupiter's Travels