Go on and off track as you wish all day... its perfect situation IMO...
Going out in sessions limits your track time and who you are out on track with, which ruins it... if you have a problem you miss out on track time... I felt the need to stay out on track for the full sessions to get my moneys worth which I feel is harder on the car despite cooling laps mid session.... only ever did one sessioned trackday which was Croft, never done one again!