Can my 20-year-old son be sponsored on a DTV visa for 5 years?

The question pertains to whether a 20-year-old son can be sponsored on a DTV visa for a full 5 years or if his visa will expire when he turns 21. Community responses indicate that dependents must be under 20 years of age, leading to uncertainty about sponsorship for a 20-year-old. Additionally, a follow-up question regarding a 17-year-old daughter suggests that her dependent visa would also be valid only until she turns 20, although one comment states that DTVs are generally issued for 5 years regardless of age limit.