A mining contract from Hashnest has no end date or expiration. This means that your hashrates are yours to mine for as long as you want, unless the market turns bad and mining becomes unprofitable.
By unprofitable, it means when the daily maintenance fees are more than your daily payouts for 10 continuous days, which is highly unlikely based on the current market (as of June 2019). If it happens, we will then announce the shut down of mining activities to prevent your further losses.
This applies to all mining contracts and/or hashrates bought from market.