I'd never go on contract ever again,
By a phone,
Talk mobile sim only 30 day contract they use Vodafone 4g v.g and I can honestly say best signal quality Ive had out the lot of them,
look after the phone front back covers,
12 months flog on and get whatever new gizmo high tech phones are out there,
you might not save bucket loads of cash but, your in control of which provider and which phone you use and your not stitched to a provider for 24 months, 24 months is a long time in the mobile phone world. I personally don't see the reason to keep upgrading other that a status message to others. If it does the job then stick with it. And repairing, my lot have iphone 5's and 6's and there a doddle to replace screens. I have a p8 lite and same again 15 minutes to change then you get S6 EDGE and above which need similar skills to open heart surgery to fix
Oh and make sure it's covered on your home insurance or add it if not just to be safe. The minutes and data with these top end phones are no more than £5-£7.50 sim only deals in disguise