The booking window closes earlier than any shop will volunteer
Most rental shops in cities like Delhi, Mumbai, and Hyderabad work on a 7-to-10-day advance booking window for standard lehenga sets. For wedding season, October through February, that window stretches to three or four weeks minimum for anything in the heavier, more embellished category. The shop will not tell you this upfront. They will show you what is available today and let you assume availability works the same way next month.