When I was planning my wedding, there was a craft store in town going out of business. We were able to buy large packages of balloons at 90% off the original price. We wanted to cover the ceiling of the reception hall with several hundred balloons and use more balloons in other areas of the room. We needed a helium tank in order to do this decorating.
After calling local businesses, I found that Praxair had the best price. We rented a tank that was about 5' tall and, even with all the extra helium my nephews used making funny voices, we did not empty the tank.
When we ran into a dilemma with returning the tank, the man we dealt with was completely flexible. Our wedding was on a Saturday and we were supposed to return the tank on Monday; however, my 5'4" mother was the only person who would be in town then. The man at Praxair understood that she wouldn't be able to maneuver the tank so he allowed us to wait an extra week until my husband and I returned from our honeymoon before returning the tank. He didn't make us pay any additional fees, either.
Working with Praxair was definitely a positive experience that I would repeat if I ever have a lot of balloons to blow up again.