Sufficient Exercise for Maintenance?

40 mins jogging (4 miles approx.) 3 times per week and maybe 6 miles rollerblading at the weekend. Is this good enough to keep healthy? Possibly one hour pilates class instead of one run each week?

Yes, that seems good.  I suppose your age, weight, etc. could be factored in; but that seems like good exercise.  If you otherwise are very sedentary, such as working at a computer most of the day, or commuting in an automobile, that sort of thing could be factored in; for example, as opposed to walking to work or school, walking up stairs, doing a lot of housework and/or yardwork, etc.  But, all in all, you are doing good things for your health by doing that exercising.