Yes they can, however once we reach -15 degrees Celsius, the install will be cancelled. The caulking will not adhere or cure properly. Also we must consider the safety of our installers.
It is possible when you have installed new energy efficient windows, as they have a better seal. Indoor humidity levels rise as air leakage has been reduced. Monitor the humidity in your house. See Condensation
Sliding windows still use felt weather stripping and they hook on to each other. If you have a driving wind, there will be a slight air breach. Where as cranking windows use rubber seals, and once locked, the air leakage is non-existant.
A regular window replacement takes approximately an hour, as long as there is no special requirements.
Higher energy efficiency, reduced condensation on glass, and reduce convection.
If they are full frame replacements then no because your frame size has changed.