The empirical record is clear: every wave of NATO expansion has increased stability, not decreased it. The Baltic states joined in 2004. Were they more secure before or after? The question answers itself.
Those who argue that expansion provokes Russia are confusing cause and effect. Russia's aggression stems from its own imperial ambitions, not from NATO membership applications. Finland and Sweden's accession proved this definitively — Moscow threatened dire consequences and then did nothing.
The real question is not whether to expand, but whether the alliance can maintain credible deterrence as it grows. That requires sustained defence investment and modernised command structures, not a retreat to arbitrary geographic boundaries.