The traditional shift run in some places is Evening, day, morning then back the same night then off off. Repeat. (1400-2300, 0900-1700, 0600-1300 same day 2300-0600 sleep that day, OFF OFF. and similar) 1 weekend off in 6. Other places have bizzare runs where you never seem to work the same sequence of shifts and have to consult your roster every day. There is a new roster system coming into use that is computerised and allocates staff that are available to cover the published hours of coverage. This will be more haphazard again.
As for Enroute to Tower, it is very very rare. TMA to Tower more likely but still pretty rare. Enroute to TMA is impossible from some groups as well (eg Tops) as you are required to go via an arrivals type function to tick the box for experience. So assuming you go to Tops or West P (which is where they seem to send all the previous experience guys), 15 years there, 7 years on something arrivals, 10 years TMA then up the pole. This all asumes your 'corporate behaviour' is up to scratch as that is now a criteria for applying for anything internal these days. Hope you are young.