For more intentional work in regulated industries, 3-5 years seems to be the minimum before things appear suspicious
Basically, if you just want to be a programmer/code-slinger and not aspire to more, then hop around all you want. If you want to be taken seriously as an engineer, then expect to serve time in a position for a while and work in the trenches with the other engineers.
I'm sure we all have read about many companies giving new recruits substantially higher pay for the same role, creating resentment amongst the existing staff.