You are limited in the number of calories for sweet treats (It's 100 now right?). And I think the purpose of that is to limit consumption of artificial sweetener. Of course, you could drink splenda-sweetened drinks all day and never hit the limit, so there is a way around it. I don't think splenda intake has specifically been limited. Generally, though, I don't think it's good to use too much. I try to limit to one or two packets/day. It does seem to cause cravings in some people, and it gives me gas if used in excess.
Life's a journey, not a destination.
It's easier to stay on plan than to get back on plan.