He has had eight jobs in management prior to this one and only stayed at one of them longer than two years (and that job he only stayed four). If that's not the sign of a short term manager, what is?
I think the problem for Spurs is that Conte wants to compete for the league. He is obsessed with winning the biggest trophies, he isn't going to be happy with top four and neither will he care about the domestic cups. But competing for the PL is incredibly hard right now with the quality of City and Liverpool, plus Spurs are basically nowhere near ready to do it. They have neither the quality in the first eleven nor the depth. Realistically, they need to add like 6 top class players (top class starting LWB, top class starting RWB, top class starting CM, top class starting LCB, very good backup striker, very good backup winger who can rotate with Son/Kulu and not see quality dip too much) and then they have to hope that a 29-year-old Kane and 30-year-old Son don't decline or start missing lots of time via injury, and then they might have a shot, but would still probably be underdogs to both City and Liverpool. That's going to take a massive outlay financially and they probably have to be willing to make some of those signings veteran players because Conte definitely prefers experience. CL will help for sure but they also already owe 80m for Romero and Kulu just to keep the team they have.