Prestige, Power & Influence

Give Players A Stake in the World
There is a reason White Box and other early editions of the World's Most Popular Adventure Game use titles to describe members of a certain class that share a level, such as all level 4 Fighting Men being known as Hero, 9th level as Lord. The title helps set a place for the PC as a member of a hierarchy within the fictional society of the game milieu.
White Box has been described as "zero to hero" reflecting the tendency of 1st level PCs to be very weak and vulnerable to damage and becoming more heroic as they advance in levels. This is a fair assessment of not only the White Box, but f all early editions of the world's most popular fantasy role-playing game when using the rules as written.  Addressing the issue of PC vulnerability, i.e. weak starting hit points, many referees have used various methods to boost those starting character HPs. So what kind of folks do the 1st level PCs really represent?  Taking the default medieval milieu into mind, the PC may be the average soldier, apprentice or cleric off on their own for the first time? A peasant of slightly better aptitude, maybe having acquired some "secret" skills now seeking their fortune away from the village where they were born? Freeborn who had the benefit of some class training who are out to make good in the world by doing heroic deeds? Perhaps the social climber who hope to prestige the American dream-story of rags to riches and sees adventuring down old tombs as the fastest way to acquire wealth and fame and the power and privilege that goes with it.
So you want to be a hero? Find a dragon to slay...a princess to rescue? That seems to be the draw that leads to a life of adventuring. Much like the gold fever of prospectors everywhere, adventurers dream of striking it big and retiring to a rich and comfortable post-adventuring life.
If they survive the delve, adventurers bring home some wealth and often enough gold is recovered to finance a nice villa, castle, tower or temple. That's what the game assumes PCs will do with their recovered fortune. And this makes them potential players in the fictional society of the game milieu. It is never too early for the referee to start playing to this end. Introduce the PCs to potential allies early on. Let them run afoul of future rivals. Encourage their hopes and dreams so that they will want to take an active part in the milieu long after they have more than enough treasure from adventuring. Moving veteran PCs into the role of patron, baron, merchant, adviser to the King or Queen (recall that princess you rescued!).
If it's adventure your party craves and you and your players have little interest in playing a different sort of game, which high level can become, you may want to offer gentle retirement as an option. This is actually my preference as a player. Retire the old PC and lets make a new one and explore his/her story. If it's old school, not every PC makes it to retirement. That is a remarkable accomplishment. Let it be so.
Character death should be a thing too. Try to make a little table drama happen whenever a PC is lost. It completes the story of that character and gives some closure for the player who is rolling up a new PC. Total party kill's should be epic...even if they aren't. As referee you have narrative control of the table, use it to dramatically end the tale of those particular PCs. Let their deaths mean something, and if possible use it as a jumping off point for the next chapter in the story. "Fifty years later a group of adventurers come upon the bodies of the slain PCs..." Those are your new 1st level player characters! Now start rolling them up.
A good campaign will outlive several generations of PCs. The world becomes the central theme that connects all the stories told of adventuring in that campaign. In this way the game becomes even more believable and real to the participants. The original game was envisioned to be all this and maybe more. Then again, maybe it is just a game about dungeon delving? It's your game, make it what you like.