If the waist band says 34, it will expand to 36.
I think they may lose some "stretch" over time as they are elastic and the jeans may shrink a little.
I just bought a pair of 44. I can stretch the waist to over 46 (almost 48) new, never worn.
I have an older pair of 44 that if I measure now are 46 but still stretch a little.
10 months ago
Lawrenceburg, IN, USA