i rode a bicycle once from Forlimpopoli (about 200km southwest of Bologna, up through Bologna, Venice, Nova Gorica (crossing into Slovenia), from there to Ljubljana, and finally to Maribor

so long as your ride is adequately comfortable you can do 7-9 hours a day and on a bicycle that's about 25km/h average between climbs and downhills i imagine on one wheel it's more like average 15km/h, i bet it's pretty scary rolling at 25, so let's say it should be possible to do about 60km/day so 15 days you should be able to easily go 900km

extreme long distance walking is fun too... i discovered that it was very comfortable to do it stepping across train sleepers while the trains were mostly not running in Serbia, i was doing about 40-50km a day, from belgrade to sofia in about 7 days