You can use Stamina for free. Premium is an optional subscription that adds three things.
Free
- Your running plan, week by week.
- GPS runs, with the watch and live on the lock screen.
- This year's history and your steps.
- Your best times for 1, 5, 10, 21 and 42 km, with your 10 best times at each distance.
- Sharing your runs.
Premium adds
- More than one goal at a time, each with its own plan. See Have two goals at once.
- Previous years of your history.
- Exporting your runs as GPX, one at a time.
What it costs
Monthly: USD 9 a month, which drops as long as you stay subscribed and activate each offer (see how the price drops). Yearly: USD 49.99 a year, which works out to USD 4.17 a month. In other countries, the price is the equivalent set by each store.
Premium belongs to your account: you pay for it on the App Store or Google Play and you have it on every phone where you sign in with that account. You activate it from Profile › Settings › Subscription.