emotional statements and subjunctive
If i wanted to say something like : You'll always have a place in my heart . I would say tú siempre tendrás un lugar en mi corazón or the subjunctive?
4 Answers
Siempre tendrás un lugar/sitio/espacio en mi corazón.
Subjunctive for ' tener ' ( 2nd from singular ): tengas, tuvieras, tuvieses, tuvieres.
We also say:
Siempre tendrás un pedacito de mi corazón / You'll always have a bit of my heart
Te ganaste mi corazón / You've own my heart
I would use "tendrás" You use the subjunctive with wishes, emotions, impersonal expressions, recommendations, and doubt.
You use is after emotional words like me gusta, me molesta, o siento. the word Siempre indicates a certainty so you don't use the subjunctive.
however I am not a native speaker and I still have a hard time with the subjunctive myself. wait for a native Spanish speaker to make sure. 
You are right: the indicative is the right answer. You are not guessing nor wishing something, but making an statement. That is why you use de indicative.
In my non-native opinion:
You are declaring that statement- it is indicative.
If you were expressing your feelings about that statement instead of declaring it then it would be subjunctive (not that my examples really are things you are that likely to say):
Me importa que siempre tengas un lugar en mi corazón.
Quiero que siempre tengas un lugar en mi corazón.
