Its the same with everything - take care of it and it will (generally) take care of you.
Personally I would swear by the GEBE kits because they are fit and forget - mostly. The problem with them is where they mount and also that you are stuck with a single ratio - there is no way of putting the output through a gearbox.
I have done probably over 450 miles on mine and all I have done is checks and put fuel in it when it needs it. I check the spark plug very rarely and the thing on my bike that has needed most attention is the front suspension..
I think for the distances you are talking about decent suspension and brakes are a must - lights as well if you are going to be riding darkside
Its actually beginning to be a bug bear with me the number of people who dont ride with lights - not even LED's - and expect motorists to see them... you can guess who will get the blame.. and its not the person on the bike..