I pioneered for four years and had seven bible studies. One of them got baptized (thankfully she has since left). When all the other bible studies ended their studies, I never felt I had wasted my time. There is nothing better for a JW than to sit and study with someone. It is so much better than pounding on doors or scaring people in the parking lots. They count the time, they count the bible study, they gain the admiration of others, they tell of the experience at meetings, assemblies, and conventions, and brag to the CO. There are no draw backs to having a bible study.
I will tell you how my studies all ended: I don't remember any of them really saying "I don't want to study any more". Most of them, appeared, to become too busy. They didn't have time to reschedule. They stopped being "home" when I called. They just kind of faded away. The car group would explain such occurrences by using the illustration from Matthew 13 about the various kinds of soil. "Oh, they got choked out by anxieties of life" or "The burning sun of persecution withered them". I never remember having hard feelings for these people, or thinking they deserved death. I remember feeling fond for every person who had given me the time and opportunity to avoid pounding on doors and to teach. I loved talking about the bible, I hated door-to-door presentations.
I hope this helps. Don't be afraid to ask for what you want.