78 days to find a replacement tenant on a 19,200 sf clear-span I thought would lease in three weeks.

78 days and $22,000 in carrying costs is a real and useful data point, and the fact that you held to $5.95 instead of taking $5.40 suggests you had enough reserve to wait it out. That discipline matters.

On your actual question: for single-tenant industrial in secondary Missouri markets (meaning markets outside the two major metros), the vacancy assumptions I see modeled most often run 90 to 120 days between tenants, with a broker co-broke built in as a line item rather than a contingency. Your 78 days was actually inside that range. The problem was your model assumed something closer to 21 days, so the gap felt catastrophic even though the outcome was not.

A few things worth knowing as you reprice future deals. The 36-month term with two six-month options is short for industrial. A typical NNN industrial lease (NNN means the tenant pays taxes, insurance, and maintenance on top of base rent, so your income is cleaner) runs three to five years on a first term. A tenant who only commits to 36 months is either credit-constrained or hedging, and that matters for what you should pay for the asset today. When you buy, the remaining lease term affects what the next buyer will pay you later.

On whether 90 days is conservative enough: it depends on the power situation. You mentioned one prospect walked because you lacked 30-amp three-phase. Do you know the cost to bring that service in? Adding it between tenancies is often more negotiable than during a tour, and it would remove a disqualifier that cost you at least one real prospect this cycle.

What's the power-upgrade cost look like for your building, and did your broker give you a number on it?

78 days in a secondary Missouri market on a single-tenant clear-span is not a horror story, it is closer to a baseline, and the 36-month term with rolling six-month options is the real number to sit with here.

The assumption doing the most work in your repricing is not vacancy duration, it is lease term risk. Your $22k carrying hit was painful but bounded. The exposure ahead is that a 36-month term with two short options gives that parts redistribution tenant an exit in roughly 30 months from now if the market softens or their parent company consolidates. You are potentially underwriting another vacancy event before you have fully recovered from this one, and if you reprice to 90 days you also need to model the probability of it happening again inside a five-year hold.

On the 90-day question: mid-Missouri is not a gateway market, so 90 days is a reasonable central estimate for a well-spec'd building in that size range, but I would not use it as a floor. The two-serious-out-of-eleven tour ratio you described suggests a thin qualified-demand pool. If one of those two prospects disappears for reasons unrelated to your asset, you are looking at 120 to 150 days on the next cycle. The three-phase power gap you encountered is also worth flagging separately: that prospect disqualified the building entirely, which means your marketable tenant universe for this box is already narrower than the raw tour count suggests. If you are buying more product in that spec range, confirm the power availability in the submarket and factor in the cost of a service upgrade as an option value item, not a surprise.

The broker co-broke cost sitting outside your model is a structural modeling gap, not a one-time error. In a secondary single-tenant market where you are likely to need representation on re-leasing, that fee belongs in your underwriting as a base case, not a contingency.

What does your current proforma look like on carrying cost as a percentage of annual NOI, and are you stress-testing at the 36-month lease expiration or running the full option period as assumed occupancy?