Speed Twin 900: What gear do you use for each speed range?

I basically have 2 questions:

1. First classic bike (Speed Twin 900). Never had one without a tachometer, so I dont really know how much the bike is working before I need to upshift. People will tell me to feel the bike. But honestly, the bike is so smooth its hard to tell when it redlining. Unlike my lower CC z400 that definitely tells when it needs to upshift.

So I just want to ask what speed range do you all shift? Are these ranges okay:
1st: 0-30kph
2nd: 30-60
3: 60-80
4: 80-100
5: 100- up?

2. Is it okay to ride a bike like the Speed Twin 900 on first gear alone for city traffic? As said above, this bike is so smooth that riding around 30kph hardly give the telltale sign of engine strain. I tend to shift between 1st and 2nd gear mostly in city. But find myself spending a lot of time on 1st gear alone because of how smooth it is. Will the engne of this type of bike wear faster if I stay on 1st alone? Honestly, its not like a sports bike where the 1st gear is jerky/twitchy and demands to shift up.