Hi Vijay kumar,
I have gone through your question,
Yes the products you are using do serve your purpose effectively, and as you said they are giving you good results, I think its no harm using them, anyway chemical medications should not be used for quite long period at a stretch .If you experience any skin darkening or irritation , i recommend you to consult your Dermatologist
immediately, if not its fine.
I would also suggest you to try certain natural remedies like applying Yogurt(=curd)+lemon bleach or pack or Aloe Vera
packs (which you get at stores) or sandalwood paste since they reduce tan quite effectively and naturally.
I Hope this answer helps you ,
Wishing you a Good Health,