XP and Leveling

Both FANTASY HACK and AD ASTRA use, essentially, the same rules for character advancement and experience points (XP)—i.e., there aren't any, and advancement happens when the GM says that it happens.  Just for the sake of "posterity", let me reiterate the rules from each:

Fantasy Hack:

Level Advancement.  Characters normally start at 1st level, but they may not at the GM's discretion, and in any case, one hopes that characters who survive their adventures get better at having them after a time. One of the fun things about playing an ongoing game is improving your character, which because of legacy and tradition is done through levels. Gaining a level, or leveling up happens at the GM's discretion, based on the pace that he wants the game to have. Personally, I prefer a pace that starts out relatively fast but slows down; i.e. moving from 1st to 2nd level takes 4-5 sessions, but advancing to the next level takes 6-7 sessions, and to third level may take 9-10 sessions, etc. 

Each level adds the following to a character:

• The maximum hit points of the character increases by 2.   

• +1 to all To Hit rolls.  

• +1 to all Skill modifiers. In addition, if the level divides by three (i.e. level 3, 6, 9) add 1 point to STR, DEX or MND. 

• Don’t forget, if you play a Fighter, you gain +1 to their attack and damage rolls at levels 4 and 8. 

• Experts gain new Affinities at 3rd, 6th and 9th level.

• For every even level that you gain, you gain a point of AC.

Although there's no reason why you can't go on from a mechanical perspective, this game is not meant to support levels above level 10. On average, at my pace, that would be at least a good 100 play sessions or more—about as long as I could possibly stand to run a single campaign and deal with the same characters anyway. 

Although it's normally presumed that all characters in an adventuring party are the same level, there are times when this will not be true, such as in the event of character death and replacement, or when a new player joins the group, etc.  Although some GMs prefer to start new characters at the same level as existing characters in the group, others do not.  If you have characters at different level, be sure and note their level in your notes (you probably want to know certain details about the characters anyway) and you may wish to track their advancement separately, to have the lower level characters advance more quickly and gradually catch up to the rest of the group.

And in Ad Astra, the rules are basically the same yet expressed slightly more briefly:

Level Advancement.  In general, characters advance when the GM says that they do, rather than against some formula of antagonists defeated. I expect in normal play to treat advancement as happening once every 4-5 sessions or so, but that can be sped up or slowed down to taste and depending on the desired length and scope of the campaign overall. I do not anticipate ever having a campaign go higher than 10th level, so it becomes an effective level cap on the game and on characters. 

Every time a character levels, he gains the following advantages.

• +2 hit points

• +1 to all attack rolls

• +1 to all skills

• On levels divisible by three (3, 6, and 9) add one point to STR, DEX or MND (except for robot characters.)  If adding a point to STR, this will also cascade to your hit point total.

• On each even numbered level, remember that your AC increases by +1 as well.

• Remember that characters with the Combat Bonus or Psionic Weapons class abilities gain an additional +1 to attack and damage at level 4 and 8.

So, you can say that I don't really have a horse in the race about XP progression and systems for it. My system is: there is no system.  I don't even have XP at all; advancement doesn't require the expenditure of XP, and there is no "earning" of XP.  XP simply doesn't exist as a currency of game mechanics anymore in either my fantasy or my space opera m20 game.  For those who want more of a classroom lecture-style discussion on why not get rid of XP entirely, you can read this post here.  Which I just found myself, but it already said everything I could want three (or more) years ago.  Granted; he uses a Pathfinder Adventure Path paradigm as his example—because that's what he plays—but the discussion isn't limited to that playstyle, as he also argues at length.  And although I disagree with it, there's a relatively thoughtful rebuttal to that article here, as well.

And yet, I can appreciate a good mechanic, or fun little whatever when I see one.  Here's an alternative, for those so inclined, to the standard XP, or to just throwing away XP entirely.

http://jasoomiandreams.blogspot.com/2015/05/good-riddance-experience-points.html