The practical side, which is where most campaigns quietly fail.
Placement beats size
Put it where the traffic is, not where it is convenient to tether. The blimp needs a clear sight line from the road your customers actually use, which is often not the road your front door faces.
At 120 feet it clears rooflines, sign clutter and most trees. Going bigger at thirty feet does not solve the same problem and costs more helium forever.
Why 120 feet
Below 150 feet above ground the FAA is not involved. Flying at 120 leaves margin and keeps the paperwork at zero.
Within five miles of controlled airspace, call the local tower and ask. In forty years we have never been refused. Johnny Mulder, who runs the company, holds an FAA commercial pilot certificate, which is why this answer is specific.
Your city sign ordinance is a separate question and worth checking.
Helium supply
Buy locally from a welding-gas or industrial-gas supplier. Do not order helium online. Expect about $300 for a 200 cubic foot tank, roughly $1.50 per cubic foot.
Ask about cylinder rental terms at the same time, because that is the cost people forget to ask about.
Knowing when to top off
At about one percent loss a day nothing fails suddenly. The envelope softens and the blimp rides lower on its tether.
Use that sag as the gauge instead of a calendar. When it stops looking taut from the road it has stopped selling. That works out to every three to seven days.
Who we are
Forty years manufacturing polyurethane advertising balloons and blimps. Some customers have been with us over thirty years, and around 40 balloons fly weekly in greater Phoenix on our equipment.
One million dollars in liability insurance, and one claim in forty years, for two thousand dollars.
More at advertisingblimps.com.