Traditionally in Japanese scorekeeping, infinitely looping games are only tracked up to 10,000,000 points, with pretty much the only exceptions being games that achieve this score in Loop 1.
Players that achieve this have their score listed as "10,000,000+α" and most of the time only the first few players to achieve this score are listed.
The exact reason for this is unknown but it likely is because most Japanese arcade score leaderboards required games to be played in an actual arcade during operating hours.
One of the most popular classic shmup developers was Toaplan.
Most Toaplan shmups were made in this style, with V-V and Batsugun being their only shmups that aren't infinitely looping.
Here's a chart showing how long this takes in each of their games.
|
Game
|
Time Estimate
|
Loop Estimate
|
|
Tiger Heli
|
8.5 Hours
|
40 Loops
|
|
Slap Fight
|
3.5 Hours
|
16 Loops
|
|
Hishouzame
|
4.5 Hours
|
20 Loops
|
|
Kyukyoku Tiger
|
3 Hours
|
4 Loops
|
|
Tatsujin
|
3.5 Hours
|
7 Loops
|
|
Hellfire
|
4 Hours
|
8 Loops
|
|
Daisenpuu
|
5.5 Hours
|
15 Loops
|
|
Zero Wing
|
3 Hours
|
3 Loops
|
|
Same! Same! Same!
|
2 Hours
|
3 Loops
|
|
Out Zone
|
2.5 Hours
|
6 Loops
|
|
Vimana
|
3 Hours
|
7 Loops
|
|
Fixeight
|
3 Hours
|
6 Loops
|
|
Tatsujin Oh
|
7 Hours
|
7 Loops
|
Notes:
Zero Wing 10,000,000+α is believed to only be possible on the 1p version through checkpoint milking.
If it is possible on the 2p version it would likely take around 5 hours and require clearing 7 or 8 loops.
Dogyuun is excluded from the list because an infinite score trick is known to exist in the game.
It also killscreens after Loop 4 and therefore tehcnically isn't an infintely looping game.
Same! Same! Same! is pretty much guaranteed to reach 10,000,000 on Loop 3, but with a No Miss 2-ALL it can be done at the end of the second loop.
Community consensus is that Vimana is the easiest game to achieve 10,000,000+α in and Tatsujin Oh is the hardest.
In some Toaplan games, it's still possible to max out the score past 10,000,000 points.
The most well known example is Same! Same! Same!, which maxes out at 100,000,000, and takes 8 hours and 12 loops in the 1 player version.
Also worth noting, in the 2 player versions, it only takes 6.5 hours and 10 loops due to a glitch that awards loop clear bonus twice.
In some games it's also popular to play past 10,000,000 even without maxing out the score, such as Kyukyoku Tiger where a popular goal is to clear 16 loops, which scores about 40,000,000 points.
Tiger Heli, Slap Fight, and Out Zone's scores max out at 9,999,990.