I'm not such a big fan of full housing, because I had a bad experience with it.
I used to have a bike with full cable housing. It was fine until it went through a winter, when the shifting got gummy. It turns out that salt and water that had entered through the back end of the housing and had no way to leave, so it caused about a foot of cable to rust. I ended up replacing the whole housing, but since none of the few-foot sections I had lying around were long enough, I had to go spend $24 on a 6-foot run of housing at the shop. With shorter segments, replacing just a part would have cost a lot less money.
From then on, I decided to use stainless cables, but given enough salt and water, even stainless can corrode. Even without corrosion, the housing can get gummy if dirt gets inside. Then you have to replace the whole thing.
Even if you use sealed ferrules on the back end, water can still get in from the front end, where the housing meets the shift lever. And once water and dirt gets in there, it stays there, so it seems to me that you'd have to replace the housing periodically anyway.
You may be able to go longer between replacements with full housing (plus a sealed ferrule at the rear) but when you do, you'll have to replace a lot more of it, so it seems like a wash to me. If you could seal up both ends, that's a different story. Then maybe you could use a cable+housing set forever.