Let's say you store all your wealth in a deflationary currency, for the obvious reason that it gains value over time. Then converting it to an inflationary currency would simply add overhead. So you would spend the deflationary currency.
1. Nobody would store all their wealth in a deflationary currency - other forms of assets, stocks etc will still exist. They will need a high liquidity vehicle to trade a.k.a inflationary currency.
2. Deflationary currency doesn't necessarily mean it will gain value overtime. Unless it contains growing intrinsic value, the overall market cap will drop/plateau.
Think of inflation vs deflation as lubricant vs sandpaper, one encourages economic activities while the other discourages.
2. Exactly which is why people would be fine spending a "deflationary" currency