I think the appeal of the base tan is to look good on your first day of holiday. Nobody wants to look like they've been inside for the last few months waiting for the snow to melt (even if it's true).
Depending on your skin colour, in general the average person can develop a base tan in 3-5 sessions which can then be maintained with regular sunbed use. Two sessions a week should be enough to further deepen your tan in a safe and gentle manner. If you simply want to maintain the tan you already have (for example, when you get back from holiday), then one session a week will probably be enough. It is very important to leave a minimum of 24 hours between each session so that your skin has the chance to rest and regenerate between sessions. We recommend leaving 48 hours. By caring for your skin in this way you can avoid burning or brown spots, which can happen if you spend too long on a sunbed or in the sun. Also, your tan will be a better colour and should last longer if you slowly build it up.
Having a base tan means the skin can be exposed to up to 4 times more in the sun before burning than without the base tan. For example, if you burn after 10 minutes of sun exposure, a base tan might mean you can be in the sun for up to 40 minutes before burning.
Because you are taking a controlled session according to your skin type and following advice given, you do not need to use SPF when using a sunbed. Using one during your session will effect your results.
Always remember to wear SPF on holiday and in natural sunlight as these rays are not controlled.