A zinc oxide or other sunscreen recommended all the time ?

Depends: Sunscreens with uv blockers can prevent sun damage to the skin in the short and long run. Chronic sun exposure can lead to skin cancers later in life as well as skin degredation giving it a coarse leathery appearance in later life. This is especially necessary if you have pale skin or live in a very sunny climate like australia.

Yes: You should be using sunscreen on at least a daily basis. Zincoxideis one of the safest and most effective active ingredients in sunscreen.