Why the number of visits matters more than the price per visit
Every visit carries three costs and only one of them is the striping. Mobilisation is charged whether the lot is 40 stalls or 400. Closing the lot costs the same whichever material is going down. So a cycle that halves the number of visits does not halve the striping bill, it halves all three, and the arithmetic tilts much harder than the price difference suggests.
With the placeholder figures, cycle A at 1,450 dollars every 18 months carries 250 of mobilisation and 400 of closure each time, so each visit is really 2,100. Cycle B at 3,600 every 48 months is 4,250 a visit but goes three times as often on the calendar rather than every year and a half. Over twelve years, discounted, that comparison is not close, and almost none of the difference comes from the paint.
Two levers, both solved rather than guessed
The first lever is price: what would cycle B have to cost per visit for the two to come out level. That is worked from the discounted visit schedule and then the entire model is re-run at that price, and the resulting present value is printed beside the original so you can see the two match. A break-even figure produced by dividing one number by another, and never checked against the model that produced it, is the most common way this kind of page ends up printing a saving that cannot happen.
The second lever is interval: how long cycle B would have to last, at the price you actually gave, to come level. That one is not solved algebraically at all, because the number of visits is a step function of the interval and jumps whenever another visit falls off the end of the horizon. It is found by walking every whole month from one to six hundred and taking the first that comes level, which is an enumeration and not an approximation.
Choosing a horizon
Short horizons produce nonsense, because the answer is decided by whether the last visit of one cycle happens to land inside the window. Twelve years gives cycle A eight visits and cycle B three, which is enough that neither is dominated by an edge effect. If the lease on the property runs five years, use five and read the result knowing that is what it means: the cost over the lease, not the cost of the lot.
What this deliberately does not weigh
Legibility. The whole reason for striping is that a driver can see where the stall is at dusk in the rain, and there is no cost model for the difference between a line that reads and a line that nearly reads. A cheaper cycle that leaves the lot ambiguous for four months before every repaint has a cost, and it lands on the tenant and the customer rather than on the maintenance budget, so it never appears on the invoice this page is built from.
Questions people ask
How often should a parking lot be restriped?
When the lines stop reading, which is a judgement about this lot rather than a schedule. Traffic volume, snow ploughing, sun exposure, surface preparation and how tolerant the tenant is all move it, and they move it further than the choice of material does. Photograph the lot every few months and you will have your own interval, which is worth more than any published one.
Is a longer lasting striping material worth the extra cost?
It depends far more on what a visit costs than on what a gallon costs. Mobilisation and closing the lot are charged whichever material goes down, so halving the number of visits saves those too. Put both intervals and both prices in and the page gives the annual cost of each, plus the price the expensive one would have to reach to come level.
What discount rate should I use?
Your own cost of money. If the choice is between spending now and spending later out of the same operating budget, something near your borrowing rate is reasonable. Setting it to zero turns the comparison into a plain sum of visits, which is often close enough over a short horizon and is easier to defend to somebody who does not want a discounted cash flow.
Why does closing the lot matter so much?
Because it is frequently the largest number on the page and it never appears on the striping invoice. Lost trade, staff moving vehicles, weekend overtime. It is identical for both cycles, which is exactly why it pushes the answer towards fewer visits, and it is the usual reason the cheap frequent option loses once somebody actually costs it.
How is the break-even price checked?
By re-running the whole model at that price and printing the resulting present value next to the original. If the two do not match, the break-even is wrong. A figure arrived at by dividing a saving by a rate and never fed back through the model is how these pages usually end up promising something the arithmetic cannot deliver.