+1
I keep a spreadsheet with date/miles, what's been done, what parts were changed. I also have the receipts for materials and I write on them the date and mileage that it was carried out, so it all correlates.
My strom came with full service history, which is to say a full set of stamps in the book, that's all.
Not main dealer stamps though. No other information... it could mean just minimal servicing (oil & filter), or fully serviced to factory spec. Luckily the only thing that is critical, I think (depending on the mileage), is the oil change frequency.
I would say to anyone building a formal service history (main dealer or not).. keep all the receipts & reports that detail work carried out & parts changed!
However I would encourage people to do there own servicing if they can, main dealers charge too much, independent bike shops can be a good alternative. However if you're competent with motorcycle then do it all yourself.
Another way to think of it is this.. how much money do you stand to save by self servicing vs how much value do you think you'll lose. I think you'll soon have saved much more than you might lose in resale value.