Starting off, they both rely their existence on one another from a simple act and interruption in time. After the events of 06 it was supposed to be no strings attached anymore, they don't know each other anymore other than a faint vision. Outside Mephiles's influence. Silver tied the knot and their strings are attached again, untying the knot will make them cease to exist, every single action done in the present affects Silver, relying on the other's each action because Silver, Silver is relying on every action the present makes, every action sonic makes because he decided to you with time. The present is no different for they are reliant on Silver himself to make a change, to show them the way to keep chasing their own future. He is a bad omen, but nothing more than a lucky charm to Sonic, for being the answer and the change to everybody, as Sonic is the reason for peace for Silver. They know every action matters and it encourages them to make a change and make a better long lasting peace.
Silver is one of the only few characters that Sonic can't just reach on a random Tuesday, he's VOCALIZED Infront of his face that he misses him, making sure he's okay and wanting to spend the most time with him in a little time he has with Silver still around. Reassuring him so that both of them could have fun without being worried, he didn't bait him with a bet to be distracted from the upcoming trouble, he provided comfort and safety for silver to live his life in the past while he still can in such short time. It's what Sonic wants, for others to live the moment and enjoy his stay, because he misses him and wants to have fun with him while he still can.
Lucky charms. They are each other's lucky charm. Silver VOCALIZES it openly that sonic is quite literally his “The moment I found you this morning I knew everything would be fine” he's not using the knowledge of the future but his own heart that Sonic being available means that everything will go out smoothly simply because he's there. And what if he's not there or diseased? Silver does not care, he won't lose hope like others and do something about it.
He will come up with all the solutions if it takes for Sonic's heart to beat again.
Silver's trust on him is DEEP to the point he won't mind going all out of Sonic because he knows only the real one would live and enjoy his challenge, if he dies? Not his Sonic. It's not that he's careless, but following his heart, and Sonic is well aware of that
Sonic doesn't label himself as a hero, Sonic hates being held still, but those dislikes cease to exist if it comes to Silver, because he knows he needs to hear it.
Silver's bluntness is.. "interesting" to others, but to Sonic it's nothing more than a surprise and a laugh. It is honesty, Sonic likes that and Silver happens to express it a little bit too much.
Silver is known for his straightforwardness, despite thinking is his ability, he acts first before thinking.
Unlike Sonic who's ability is to run straight ahead he is able to think first, both complementing each other's mindset and abilities.
In conclusion, Sonic maintains peace and if he doesn't, Silver's there to help him get that peace back, Sonic maintains hope, and if all hope is lost and Silver's there to bring it back, for the future and the present all because Silver interrupted time.
+ if I have a quarter for everytime silver saved Sonic's life through going super I'd have two but it's strange it's happened twice.