1. Repaint every four years.
P 
$5.12 

{t(PS)/n}(P/A, i%, n) 
$1.87 

(1t)(X)(P/F, i%, n) 
$2.11 
n=4 
(1t)(X)(P/F, i%, n) 
$1.55 
n=8 
S(P/F, i%, n) 
0 

PW 
$6.91 

A 
$0.917 /m^{2} 
2. Biennial touchups instead of repaints every four years.
Biennial touchup costs (X) at 2, 4, 6, 8, and 10 years can be expressed as an equivalent annual touchup cost X’ with the following Equation:
X’ = X[(P/F, 8%, 2y) + (P/F, 8%, 4y) + (P/F, 8%, 6y) + (P/F, 8%, 8y) + (P/F, 8%, 10y)](A/P, 8%, 12 y)
(P/F, i%, n) 
n 
0.857 
2 
0.735 
4 
0.630 
6 
0.540 
8 
0.463 
10 
and X' = 0.4281 X
Repainting costs alone can be expressed similarly with the following formula:
A = P[(P/F, 8%, 4y)+ (P/F, 8%, 8y)](A/P, 8%, 12 y)
or $0.866 /m^{2}
To be equal or less costly the annual equivalent annual cost of touchups should be equal or less that the repaint program, and hence:
0.4281 X = $0.866 and X = $2.024