Just to play devil's advocate on the upgrade timing:
If we upgrade smoothly and persistently, as units increase in power there is a small chance we'll achieve an Average military compare to KISS. The key is that our Hoplites have 1 more defensive point than spearmen. It would take about 6 more hoplites (rough estimate) than spearmen, all else being equal, to push us up to Strong. But the more assault units they have, the lesser the effect of our Hoplite numbers.
What I'm getting at: KISS is Strong now, but if they are only Average at turn 104, they may be less likely to start a war. Of course, they may realize that they will lose the advantage if they wait any longer, but still, there is a small chance that our numbers could become a deterrent to attacking.
If we upgrade smoothly and persistently, as units increase in power there is a small chance we'll achieve an Average military compare to KISS. The key is that our Hoplites have 1 more defensive point than spearmen. It would take about 6 more hoplites (rough estimate) than spearmen, all else being equal, to push us up to Strong. But the more assault units they have, the lesser the effect of our Hoplite numbers.
What I'm getting at: KISS is Strong now, but if they are only Average at turn 104, they may be less likely to start a war. Of course, they may realize that they will lose the advantage if they wait any longer, but still, there is a small chance that our numbers could become a deterrent to attacking.